Calcaholic Updates
What is new here: calculator launches, data refreshes, and improvements worth knowing about, newest first. When the numbers, formulas, or tools change, we say so.
Follow by RSS, or read how we verify our calculators.
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The Mean Value Theorem calculator no longer finds a c that is not there
Run abs(x) over an interval spanning zero and the old page reported c = 0 and declared the theorem satisfied. It is not: abs(x) has a corner at zero, its derivative jumps from minus one to plus one without ever equaling the average rate, and no c exists. The scan now tells a genuine crossing from a corner's jump by checking whether the derivative agrees with itself at two step sizes, and a corner falls through to an honest explanation of why the theorem's promise does not apply. Smooth functions are untouched: sin(5x) still finds all five of its crossings.
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The p-value calculator's display can no longer contradict its own verdict
The three most famous numbers in statistics all hit the same wall: z = 1.96 has a true two-tailed p of 0.049996, which rounded to a displayed p = 0.0500 sitting directly above a sentence calling it significant at the 0.05 level. The same thing happened at z = 2.576 against 0.01 and at z = 1.645 one-tailed. When rounding would land the display exactly on a threshold the verdict says p is strictly below, the page now shows six truncated decimals instead, so the number you read can never cross the line it is being compared against.
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The period calculator now refuses dates that do not exist
February 30 used to be silently accepted, rolled forward into early March, and used as the anchor for a confident six-cycle forecast. Dates are now checked digit by digit, so an impossible date is refused instead of quietly corrected into a different one. A real leap day still works in a leap year and is refused in a common year, which is exactly the distinction a calendar tool owes you.
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The autonomous truck page catches up with Aurora's summer
Aurora reached nearly 440,000 driverless miles by the end of June, up from the 250,000 the page previously quoted, with second-generation driverless trucks on ten routes and customers signed for 500 vehicles. The honest arithmetic is unchanged and now reads even more clearly: 440,000 clean miles is still under one percent of the 61 million a human-driven fleet averages between fatal crashes, so the record proves the trucks are real and hauling freight, not yet what their crash rate is. Kodiak's driverless deployment and Tesla's Semi autonomy timeline are also brought current.
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The robotaxi pages re-checked against September's fare landscape
Tesla's Austin pricing has not moved since the pair of March changes that landed on 3 dollars base plus 1.40 a mile, which is the structure both pages already carry, and the Waymo comparison figures we quote are still what current studies report. Two things did move. Tesla's September 3 launch event opened a search for fleet Cybercab purchase interest, a real shift the owner page now names, though there is still no consumer price, configurator, or delivery date. And Uber's reported take dipped to 25.4 percent in mid 2026, but that is a UK accounting reclassification rather than a price cut, and Uber says the underlying rate is unchanged, so the 30 percent default stands with its provenance now explained on the page.
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The AdSense revenue table re-verified against Google's live figures
All 75 cells of the category and region revenue table (25 content categories across three regions) were compared against the data Google's own estimator loads today, and every value matches what we published in August. Home and Garden in the Americas still stands alone at 13.37 dollars per thousand visits, four times Finance. This table sits on a marketing page Google can revise without notice, which is exactly why we re-check it instead of assuming.
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The retirement withdrawal calculator is more honest at equal rates
When your withdrawals grow with inflation at exactly the rate your savings earn, the balance can look magnificent at year 50 and still be doomed: the real value of each withdrawal never shrinks, so the money runs out with certainty, just far beyond the chart. The page used to say it never would. Now the word indefinitely is reserved for inflation strictly below your return, and the equal-rates case says what is true: this plan outlasts any 50-year horizon, not every horizon.
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New: Birthday Money Calculator
What a share of a child's yearly birthday money becomes if invested: pick 10 to 100 percent, see it at 18, 30 and 65, and meet the birthday dollar rule.
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New: Latte Factor Calculator
What a daily latte, Coke or any small habit becomes invested in the S&P 500 instead, priced with real market history, a chart to scale, and no lecture.
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New: Coordinates Converter
Convert GPS coordinates between decimal degrees, degrees minutes seconds, and decimal minutes. Paste any format, get all three, with the arithmetic shown.
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New: Radians to Degrees Calculator
Convert radians to degrees and back, with exact answers for pi multiples like 2pi/3, the working shown, and why calculus refuses to run on degrees.
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New: 50/30/20 Calculator
Split your take-home pay into the 50/30/20 buckets and compare your real spending against the rule, treated as a flashlight for your money, not a report card.
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New: Emergency Fund Calculator
Size your emergency fund from essential monthly expenses, not income, then get an honest timeline with milestones on the way to full cover, not just the wall.
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New: HYSA Calculator
Work out what a high-yield savings account earns on your balance, and what staying at your current rate costs you, using rates verified in August 2026.
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New: APY Calculator
Convert a nominal interest rate to APY or an APY back to the rate behind it, at any compounding frequency, with the compounding question priced in dollars.
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New: Savings Calculator
Project what your savings grow to, how long a goal takes, or the monthly deposit a goal needs, with APY converted the way banks actually credit interest.
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New: Voice Typing Calculator
Work out how much time dictation actually saves you against typing, once editing and the share of your day you spend writing are both counted in.
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Clearer answers on the loan and sales tax calculators
Both headlined a bare dollar figure. On a sales tax page showing a net price, a tax amount and a total, a naked number leaves you guessing which one you are looking at, and the headline is also the text people share. They now say what the number is. The sales tax page also prices the mistake it exists to prevent: removing tax from a receipt total is a division, not a subtraction, and subtracting the rate instead leaves you 68 cents short on a 108 dollar receipt.
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The mortgage calculator now tells you when PMI is missing from your total
It promised your full monthly payment while mentioning only in an FAQ that private mortgage insurance was left out. For a buyer putting 10 percent down that promise was short by 90 to 450 dollars a month. The calculator already knew your loan-to-value, so it now says so in the result, prices the likely range, shows what the real monthly figure would be, and tells you how much more down payment would clear the 20 percent line and remove it. PMI stays out of the headline number because the actual premium depends on your credit score, the loan type and the lender, and one invented figure in the middle of a budget is worse than an honest range.
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Post oak joins the tree age calculator, with a range instead of a factor
No growth factor table anywhere lists post oak. The US Forest Service does publish the measurement one is made from: ten-year diameter growth of less than two inches, and as little as half an inch in central Oklahoma. Inverted, that is a growth factor between 5.0 and 20.0. Every published table stops at 8, which is where post oak is only getting started, and is why the Cross Timbers hold trees far older than they look. A trunk you could put your arms around can be two or three centuries old.
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The tree age calculator now covers 70 species and three published tables
Up from 22 species and two tables. The new northeastern table adds about fifty trees, including many Southern natives: sweetgum, black gum, persimmon, sycamore, hackberry, eastern red cedar, and the mockernut and pignut hickories. Every result now shows all three tables side by side so you can see how much agreement is behind the answer. Deliberately still missing, and now said out loud on the page: post oak, loblolly pine, live oak, pecan, bald cypress and western red cedar have no published growth factor from any source we could find, and Texas A and M Forest Service reports the same limit in its own tree app. Inventing one would be manufacturing data.
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New: Subnet Calculator
Enter an IP and a mask or CIDR prefix to get the network, broadcast, usable host range and wildcard, with the binary AND shown step by step.
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New: Time Calculator
Add or subtract hours, minutes and seconds, or move a clock time forward and back. Shows the working, gives decimal hours for timesheets, and tells you when the answer crosses midnight.
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New: Retirement Spending Calculator
Work out how much you can spend each year from your retirement savings, comparing the 4 percent rule against spending down and against a fixed percentage.
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New: Tree Age Calculator
Estimate a tree's age from its trunk using the growth factor method, across 70 species and the three published tables, which disagree by up to 1.68 times.
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New: kVA Calculator
Convert between kVA, kW and amps for single or three phase at any voltage and power factor, with the square root of 3 and the generator rating both explained.
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New: Freelance Rate Calculator
Work out the hourly rate you need as a freelancer once unbillable hours, self-employment tax, unpaid time off and your own benefits are all counted in.
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New: Semester Grade Calculator
Combine your quarter grades and semester final into one semester grade, on your school's scale. Leave the final blank and it solves backwards for the score you need, with the working shown.
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2025 long-term care costs re-verified against CareScout
All five national medians were checked against the CareScout Cost of Care Survey again: 35 dollars an hour for a home health aide, 95 a day for adult day care, 6,200 a month for assisted living, 315 and 355 a day for a semi-private and a private nursing room. All five confirmed. The adult day annual figure assumes five days a week, which is our assumption rather than the survey's, and the page now says so.
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A freelance rate is about 2.6 times salary divided by 2,080
Unpaid holiday, unbillable hours, both halves of Social Security and Medicare, and the benefits an employer used to buy all have to fit inside the rate. On typical numbers replacing a $100,000 salary needs about $123.58 an hour, not $48.08. The new freelance rate calculator also shows that the billable share, not the tax, is the number that moves the answer most.
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The 4 percent rule leaves a lot of money unspent, and now you can see how much
On ordinary assumptions a $1,000,000 portfolio following the 4 percent rule finishes thirty years with about $435,000 still there. That is the premium paid for surviving the worst run in the historical record, and it costs about $9,000 a year of spending you did not do. The new retirement spending calculator shows the 4 percent rule, spending down, and a fixed percentage side by side.
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A 100 kVA generator is an 80 kW generator
Generator sets are rated at 0.8 power factor by convention, so a machine sold as 100 kVA is offered as 80 kW. Add up a load schedule in kW and shop for a generator with the same number on it and you buy one 25 percent too small. The new kVA calculator prints both figures side by side, and explains that the square root of 3 in three-phase work is geometry rather than a safety margin.
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Naegele's rule now handles the month ends correctly
Subtracting three months from a date like 31 May asks for 31 February, which does not exist, and the old arithmetic silently rolled it forward to 3 March. Four of ten sampled start dates hit it. The rule now takes the last day of the month instead, which is the convention and also the reading that keeps it agreeing with the plain 280-day count.
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Naegele's rule gives 280 days less than half the time
Every textbook glosses the rule as adding 280 days. Run across all 1,461 start dates in a four-year span it lands on exactly 280 only 44 percent of the time, and it is never shorter, only longer, by up to three days. The page now shows the full distribution and explains why the calendar causes it.
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Every grade calculator now asks which grading scale you use
Schools genuinely disagree about where an A begins, so a 91 percent can be an A- or a plain A or a B depending entirely on the syllabus. All seven grade and GPA tools now offer the three scales that actually differ, name the cutoff your number cleared, and show the full working step by step with your own figures in it.
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High school GPA now counts credits
The high school GPA calculator averaged by course count and ignored credit hours, which gave the wrong answer for anyone with half-credit electives or double-period lab sciences. It now weights by credits, defaulting to one per class so the simple case needs no extra typing.
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Age calculator no longer reports negative days
Born on 31 January and measured on 1 March, the old arithmetic returned one month and minus two days, because it borrowed 29 days from February against a shortfall of 30. It now counts forward from the anniversary instead, so the leftover days cannot go negative at a month end.
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The minus-two rule for subnets stops being true at /31
Almost every explanation of subnetting teaches total addresses minus two, and it holds down to /30. A /31 has no network or broadcast address at all, so both its addresses are usable, which is what RFC 3021 defines it for. Apply minus-two there and you get zero usable hosts, and on a /32 you get minus one. The new subnet calculator handles all three cases separately.
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A tree's age depends on where it grew up, by up to 1.68 times
There are two respected sets of tree growth factors in circulation and they disagree. Neither is wrong: one was measured on lawn and street trees, the other on old-growth woodland where a sapling waits decades in shade. For a red oak the same trunk means about 76 years or about 128. The new tree age calculator asks which yours is, which almost no tool does.
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Every 2026 tax bracket re-checked against the IRS document itself
All 21 bracket thresholds, the three standard deductions and both child tax credit figures were read out of IRS Revenue Procedure 2025-32 rather than a secondary table. All correct. The Revenue Procedure also publishes the running tax total at the foot of each bracket, so the calculator now proves its own arithmetic against the IRS in eighteen places on every build. Worth knowing: the head of household 24% and 32% thresholds sit exactly $25 below the single ones, while the 22%, 35% and 37% lines are identical, which is what makes those two easy to lose when a table is copied.
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New: Commute Cost Calculator
Work out what commuting really costs against working from home, in cash and in hours. Handles the mileage assumption honestly, counts lunch as a difference, and prices the time nobody adds up.
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New: Factoring Calculator
Factor polynomials and whole numbers with every step shown and named. Handles common factors, difference of squares, trinomials, cubes and grouping, and says plainly when something will not factor.
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New: AdSense Calculator
Estimate Google AdSense earnings from your pageviews using Google's own published per category figures, all 25 categories and 3 regions, with your real RPM alongside the estimate.
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New: RPM Calculator
Work out engine rpm from road speed, tyre diameter and axle ratio, or solve for any one of them. Also does belt and pulley drives. Shows where the famous 336 constant comes from.
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New: MTG Land Calculator
Work out how many lands your deck needs from your own mana curve, computed from the hypergeometric distribution. Shows what that count actually delivers on every turn, not just the number.
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New: CPM Calculator
Work out CPM, total cost or impressions from any two of them, then the three things a CPM hides: how many people you actually reached, how many impressions were viewable, and what a click really cost.
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New: Percent Yield Calculator
Work out percent yield, or start from a balanced equation: it finds the limiting reactant, the theoretical yield, what is left over, and your percentage.
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New: Acceleration Calculator
Fill in any three of starting speed, final speed, acceleration, time and distance. The other two follow, in your units and in g, with a consistency check.
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New: Liters to Gallons Converter
Convert liters to gallons with the exact factors for both gallons. The imperial gallon is 20 percent larger than the US one, which is the mistake this page prevents.
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New: Law of Sines Calculator
Solve a triangle with the law of sines. Handles two angles and a side, and the ambiguous SSA case where the same measurements fit two different triangles.
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New: Ohms Law Calculator
Enter any two of voltage, current, resistance and power to get the other two, with the rearrangement shown and a built-in consistency check.
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New: Molar Mass Calculator
Enter any chemical formula for its molar mass, percent composition, and grams to moles. Uses IUPAC atomic weights and tells you how many digits are real.
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New: Square Feet to Acres Converter
Convert square feet to acres and back. An acre is exactly 43,560 square feet, a number that comes from medieval ploughing rather than anything tidy.
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New: Kinetic Energy Calculator
Enter any two of mass, speed and energy to solve for the third. Any units, plus potential energy, and a table showing why double the speed is four times the energy.
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New: Force Calculator
Solve F = ma for any variable, or find weight on any planet. Newtons, pounds-force, slugs and the pound-mass trap explained properly.
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A physics cluster to go with the chemistry
Seven new mechanics and waves calculators. The acceleration one is a full kinematics solver rather than just a change in speed over time, so any three of the five quantities give you the other two. Each page carries one thing worth knowing: why doubling your speed quadruples your braking distance, why a crumple zone works, why 45 degrees is the wrong throwing angle for almost everyone, and why a torque wrench with an adapter fitted quietly over-torques the bolt.
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Science is now its own category
Chemistry and physics have outgrown the Math hub, so they have a home of their own: fifteen calculators covering molar mass, molarity, dilution, half-life, gas laws, forces, energy, momentum, projectiles, waves and torque. Nothing moved URL, so every existing link still works. The common thread is precision that is honest about itself, from IUPAC atomic weights carrying their published uncertainties to a projectile page that says out loud when ignoring air makes its answer an upper bound.
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Four electrical calculators, and a correction about the NEC
Ohm's law, voltage drop, watts to amps and the resistor colour code have joined the DIY hub, which is now grouped rather than one long list. The voltage drop page carries a correction worth knowing: the familiar 3% limit is an Informational Note in the NEC, and 90.5(C) says informational notes are not enforceable requirements. It is excellent practice that some jurisdictions have adopted as law and many have not, which is a more useful thing to know than either half on its own.
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New: Sample Size Calculator
Work out how many people you need to survey for a given margin of error and confidence level, with the finite population correction and every step shown.
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New: Gas Law Calculator
Solve Boyle's, Charles's, Gay-Lussac's, Avogadro's, the combined and the ideal gas law. Pick your law, leave one box blank, and see every step of the work.
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New: MTG Manabase Calculator
Work out how many colored sources your deck needs to cast a spell on curve, computed straight from the hypergeometric distribution with every assumption shown.
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New: Projectile Motion Calculator
Range, peak height, flight time and impact speed from any launch. Works out the best angle for your launch height, which is almost never 45 degrees.
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New: Voltage Drop Calculator
Voltage drop in volts and percent for any AWG or kcmil run, plus the max length and the size that passes. And the truth about the 3% rule.
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New: Binomial Distribution Calculator
Exact binomial probability for a fixed number of independent trials. Every tail, the mean and variance, and an honest note on when the normal approximation is safe.
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New: Hypergeometric Calculator
Exact hypergeometric probability for drawing without replacement. Gives every tail, the mean and variance, and shows how far a binomial answer would have been out.
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New: Resistor Color Code Calculator
Decode 4, 5 and 6 band resistors, or go the other way from a value to its colours. Checks whether your reading is a real preferred value.
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New: Molarity Calculator
Solve for mass, volume or concentration. Molarity, molality, normality and percent solutions, with the molar mass worked out from your formula.
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New: Roth 401(k) Calculator
Compare a Roth 401(k) against a traditional one on what you actually get to spend, including the tax saving most comparisons quietly forget to invest.
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New: Wavelength Calculator
Convert between frequency and wavelength for light, sound or any wave. Gives half and quarter wavelengths, photon energy, and the spectrum band.
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New: Dilution Calculator
Solve C1V1 = C2V2 for any value and get the full recipe: stock, diluent to add, and final volume. Serial dilution mode with the 1:10 ambiguity settled.
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New: Price Elasticity of Demand Calculator
Work out price elasticity of demand with the midpoint formula, see what your price change did to revenue, and find how much volume you can afford to lose.
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New: Momentum Calculator
Momentum, impulse and collisions. Work out impact force from how long a crash lasted, and see why doubling the stopping time halves the force.
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New: Credit Utilization Calculator
See what utilization your card will report, and work out what to pay before your statement closing date. Explains why the closing date and the due date do different jobs.
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New: Watts to Amps Calculator
Convert watts to amps or amps to watts for DC, single-phase and three-phase AC, with the power factor most converters silently ignore.
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New: Half-Life Calculator
Solve for amount remaining, elapsed time or half-life, with 13 isotope presets. Plus radiocarbon dating and the half-life labs still use on purpose.
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New: Turkey Cooking Time Calculator
Work out how long to roast your turkey at 325F, stuffed or not, and how many days ahead to start thawing it. Working backwards from dinner is the useful part.
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A chemistry cluster, built on one verified periodic table
Five new chemistry calculators share a single set of IUPAC standard atomic weights, and each one's test suite compares its copy against the others so they cannot drift apart. Two things they do that most chemistry calculators do not: they tell you how many of the digits in a molar mass are actually supported by the published uncertainties, and they say when your compound contains one of the fourteen elements whose atomic weight is no longer a single number at all.
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New: Torque Calculator
Solve torque, force or lever length in N.m or lb-ft, and get the wrench setting correction for an in-line adapter that most people never apply.
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New: Law of Cosines Calculator
Find a missing side or angle with the law of cosines. Enter three sides, or two sides and the angle between them, and get every step worked with your numbers.
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New: Significant Figures Calculator
Count significant figures, round to any number of them, and do arithmetic with the right rule. Handles the trailing-zero ambiguity honestly.
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New: CM to Feet Converter
Convert centimetres to feet and inches with the exact 2.54 factor. Gives the proper feet-and-inches reading, not the decimal that people mistake for it.
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MTG opening hand odds: mulligan as deep as you like
The mulligan field was capped at 3, which is a Standard player's assumption. It now goes as deep as your hand size allows, because a Vintage Dredge player chasing Bazaar of Baghdad will happily ship to four. There is also a switch for pods that grant one free mulligan, and the page is honest that a free mulligan makes the search cheaper without making it any more likely to succeed.
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New: Ounces to Cups Converter
Convert ounces to cups both ways: fluid ounces are exactly 8 to the cup, but ounces by weight depend entirely on what you are measuring. Both handled here.
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Space travel times now take miles and mph
Custom distances can be entered in miles alongside kilometers, AU and light-years, and custom speeds in mph. Every result echoes what you typed in your own unit before restating it in kilometers, so you can see exactly what the math received.
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Clearer fee calculators for Etsy and eBay sellers
Both pages now say plainly that every fee is charged to the seller and comes out of your payout, and the helper text under each field has been cut back to the lines that actually tell you something. A box labelled Item price did not need a sentence explaining what an item price is.
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New: Grams to Ounces Converter
Convert grams to ounces and back with the exact defined factor, plus the troy ounce used for gold and silver, which is 9.7 percent heavier and catches people out.
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New: Bigger Boat Calculator
How big a boat do you actually need for a great white shark? Worked from a published NOAA length-to-weight study and real naval architecture. The Orca was 42 feet. It needed about 59.
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New: Lottery Jackpot Calculator
Lump sum or annuity? Compare both lottery payout options after real federal and state taxes, invested year by year, and the break-even return that decides it.
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Large numbers now add commas as you type
Money fields across every calculator now group digits while you type, so 905000000 reads as 905,000,000 instead of a zero-counting exercise. The math and shared links still use clean digits underneath.
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New: Party Alcohol Calculator
How much alcohol to buy for a party, as cases, bottles and kegs. Two drinks the first hour, one after, split across beer, wine and spirits, always rounded up.
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New: Expected Value Calculator
Free expected value calculator for trades and bets: EV per trade after costs, the break-even win rate you need, and how many trades prove an edge.
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New: Tent Size Calculator
The tent size your event actually needs, named as a real rental size: guest count, seating style, plus the dance floor, bar, and buffet space people forget.
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New: Generator Size Calculator
Tick what you want to keep running and get a specific generator size in watts, with the starting surge counted properly and an honest run time per tank.
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New: BBQ Meat Calculator
How much meat per person for a BBQ, in raw pounds you can actually buy. We divide by each cut's cooked yield, because a brisket loses about half its weight.
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New: Burn Rate Calculator
Free burn rate and runway calculator. Get your monthly burn, months of runway, the deal frequency that breaks you even, and the odds of a dry spell.
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New: Cake Serving Calculator
How many servings a cake gives, worked from pan geometry against the industry chart. Wedding and party slice counts side by side, tiers, sheets, and guests.
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New: Dumpster Size Calculator
What size dumpster you need, worked both ways: the cubic yards your project makes and the tons it weighs, plus the weight limit that decides the final bill.
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New: Storage Unit Size Calculator
Get a specific storage unit size from your home size or your actual item list, worked in cubic feet, including what a walkway costs you in space and in rent.
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New: HOMA-IR Calculator
Work out HOMA-IR from a fasting glucose and a fasting insulin, in mg/dL or mmol/L, with HOMA-B and QUICKI, the working shown, and honest reference ranges.
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New: Moving Truck Size Calculator
Get one specific moving truck size from your home or item list, sized on the truck's weight limit as well as its cubic feet, because payload runs out first.
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New: Risk of Ruin Calculator
Enter your win rate, reward to risk ratio, and percent risked per trade to get your chance of ruin, plus the same edge priced at five position sizes.
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New: Kelly Criterion Calculator
Free Kelly criterion calculator: optimal bet size from your win rate and payoff odds, plus half Kelly, quarter Kelly, and the growth you give up.
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New: Investment Growth Calculator
Project what your investments could grow to, with fund fees priced in dollars, inflation, and an honest range instead of one smooth curve. Free and instant.
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New: Porta Potty Calculator
How many porta potties you need, worked from the portable sanitation industry's own chart: crowd size, event hours, alcohol, ADA units, and hand wash stations.
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New: Vending Machine Calculator
What a vending machine really profits: gross sales down through the location commission, stock, card fees, and driving, plus the months until it pays back.
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New: Etsy Fee Calculator
Every Etsy fee comes out of the seller's payout. Enter your price, shipping, and materials to see the full fee stack, what you keep, and your true margin.
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New: Pressure Washing Calculator
Price a pressure washing job three ways, see what you keep after chemicals, driving, wear, insurance and taxes, and check any quote against market rates.
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New: eBay Fee Calculator
Every eBay fee is charged to the seller: final value fee, per order fee, ad fee. See the whole stack and whether your flip actually made money after costs.
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New: Tutoring Income Calculator
What tutoring actually pays: the waterfall from your hourly rate through the platform's cut, prep time, and self-employment tax down to your true hourly.
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New: KDP Royalty Calculator
What does self-publishing really pay? Enter your format, list price, and file size or page count for your exact KDP royalty per copy, plus both price cliffs.
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New: YouTube Money Calculator
How much does YouTube pay? Creators keep 55% of watch page ad revenue. Enter your monthly views and niche for an honest earnings range, not a fantasy figure.
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New: Rover Calculator
What Rover pet sitting and dog walking really pay: the honest waterfall from booking total through Rover's 20 percent cut, supplies, and self-employment tax.
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New: Trump Accounts Calculator
Project a Trump Account to age 18, split the balance into the federal $1,000, your contributions and growth, then compare it after tax against a 529.
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New: EV Semi Emissions Calculator
See what an electric semi saves: honest CO2 math with grid emissions counted, plus the NOx and soot in portside neighborhoods that go to zero at the tailpipe.
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New: DIC Calculator
2026 DIC calculator for surviving spouses and children: screen the eligibility paths, including the 10 year rule, and see what you may be eligible for tax free.
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Sitewide instant search and reorganized category pages
Every page now has a search button in the header (or press the slash key) that finds any of our 206 calculators as you type. Big category pages are organized into titled sections with jump links, so Finance reads as Mortgages, Loans, Retirement, and Taxes instead of one wall of 67 tiles. The homepage shows each category's most-used tools with a link to the full list.
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New: Rack Cooling Calculator
How much cooling does a server rack need? Convert the rack's power draw into BTU per hour, tons of cooling, and airflow CFM, plus the power to run the AC.
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New category: Tech and Innovation
EVs, AI, and spaceflight were scattered across Fun, Finance, and Math. They now have a home of their own: EV savings and emissions, robotaxi economics, AI energy use, LLM API costs, and rocket delta-v all live under Tech, with data center, robotics, and space tools on the roadmap. Every calculator URL is unchanged.
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New: VA Survivors Pension Calculator
VA Survivors Pension calculator with 2026 rates: MAPR minus countable income, the medical expense deduction, Aid and Attendance, and the net worth limit.
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New: Space Travel Time Calculator
How long to reach the Moon, Mars, or Proxima Centauri at any speed, from a car to light itself, plus the honest 1 g flip and burn with relativity included.
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New: Turo Calculator
Would renting your car on Turo pay? The honest net after Turo's split, per-mile wear, and cleaning, plus whether it may cover your monthly car payment.
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New: Solve for X Calculator
Type an equation like 5x^2 + 3 = 83 and get every solution with the work shown line by line. Linear and quadratic, both roots always, checked by substitution.
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New: EV Savings Calculator
See what switching to an EV saves on fuel: gas vs charging cost per year and per mile, plus honest CO2 math with your grid's emissions counted.
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New: Robotaxi Cost Calculator
At what price per mile does a robotaxi beat owning a car? Honest break-even math with AAA cost figures: marginal cost vs full cost, target fares vs real ones.
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New: EV Range Calculator
See what your EV really delivers in cold, heat, and highway driving: an honest real-world range from the EPA sticker, with battery age and a planning buffer.
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New: EV Road Trip Calculator
How many charging stops your EV road trip needs, how long they add, and what DC fast charging costs. The 10 to 80 leg math, shown step by step.
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New: Order of Operations Calculator
Free order of operations calculator that walks any expression one step at a time, and shows both defensible answers to viral problems like 8/2(2+2).
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New: Robot vs Labor Cost Calculator
When does automation beat a wage? Honest robot payback math: installed cost, BLS burdened labor, utilization sensitivity, and the break-even robot price.
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New: Orbital Period Calculator
Find any orbit's period and speed with Kepler's third law. Pick Earth, the Moon, Mars, Jupiter, or the Sun, enter an altitude, and see every step of the math.
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New: Robotaxi Owner Calculator
Would owning a robotaxi pay off? Fleet income after the platform take, deadhead miles, wear, and insurance, priced against the car's real yearly cost.
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New: RAID Calculator
Pick a RAID level and enter your drives to get usable capacity in TB and TiB, efficiency, and honest fault tolerance, with every level compared side by side.
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New: UPS Runtime Calculator
How long will your UPS run on battery? Enter battery specs or two spec-sheet points and your load for an honest runtime with every derating shown.
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New: Airbnb Calculator
Free Airbnb hosting calculator: see what renting a spare room really nets per month after Airbnb's fee, cleaning, and utilities, with honest occupancy math.
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New: File Transfer Time Calculator
How long will a download or transfer take? Enter file size and connection speed for an honest time with the bits vs bytes factor of 8 and overhead counted.
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New: GPU Cluster Power Calculator
How much power does a GPU cluster need? From one RTX 4090 to 100,000 H100s: honest megawatts, annual energy, electricity cost, and CO2, every factor sourced.
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New: EV Charging Time Calculator
How long to charge your EV: enter battery size, charge window, and charger power for an honest time with real-world losses and the 80 percent taper counted.
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New: Food Delivery Pay Calculator
What DoorDash and Uber Eats really pay after the car, gas, and self-employment tax: the honest gross to net waterfall, and the bike that changes the math.
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New: Data Center Power Calculator
How much power does it take to run a data center? Enter IT load and PUE to get facility megawatts, annual energy, the yearly electricity bill, and CO2.
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New: Autonomous Truck Safety Calculator
What would autonomous semis' safety claims mean if they hold? Verified federal truck-crash baselines, your assumption on the dial, skeptic's zero included.
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New: Gold Calculator
Weigh your scrap gold, pick the karat, and get its melt value at today's spot price, plus the honest table of what pawn shops and refiners actually pay.
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New: Children's Sleep Calculator
Enter your child's age and wake-up time to get the AASM recommended sleep hours (endorsed by the AAP) and a computed bedtime window, infants to teens.
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New: Car Loan Calculator
Your real monthly car or auto loan payment: price, down payment, trade-in (even with a loan on it), sales tax and fees, priced across 36 to 84 months.
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New: Take-Home Pay Calculator
Estimate your 2026 net paycheck: salary, filing status, 401(k), and health premiums in; federal tax, Social Security, Medicare, and take-home pay out.
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New: WNBA Win Probability Calculator
Turn a WNBA point spread or moneyline into a win probability, with an honest sigma assumption, a sensitivity range, and vig removal for a fair number.
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New: NFL Win Probability Calculator
Turn an NFL point spread or moneyline into an outright win probability: the classic Stern normal model, vig removal, and the key numbers 3 and 7 explained.
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New: Rent vs Buy Calculator
Compare the true net cost of buying and renting over the years you expect to stay: equity after selling costs, the invested down payment, break-even year.
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New: Calorie Calculator
How many calories should you eat a day? Get a daily target for losing, maintaining, or gaining weight from the Mifflin-St Jeor equation, with safety floors.
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New: AFT Calculator
Score your Army Fitness Test on the official June 2025 scales: all five events, general and combat standards, and exactly what you still need to pass.
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New: BAH Calculator
Free 2026 BAH calculator with the complete official DoD rate table: every Military Housing Area, every paygrade, with and without dependents, tax-free.
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New: Odds Calculator
Free odds converter: American, decimal, and fractional formats, implied probability, payouts for your stake, and two-sided vig removal to find the fair price.
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New: NBA Win Probability Calculator
Turn an NBA point spread or moneyline into a win probability: the classic normal-margin model with a 12 point sigma, plus vig removal for fair market odds.
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New: NHL Win Probability Calculator
Turn NHL moneylines into fair win probabilities with the fee removed, or model a game from expected goals with honest Poisson math, overtime included.
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New: Golden Ratio Calculator
Free golden ratio calculator: find the golden partner of any length, split a whole at the golden section, or test how close two numbers come to phi = 1.618.
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New: MAP Calculator
Work out mean arterial pressure from any blood pressure reading. MAP = (SBP + 2 x DBP) / 3, shown step by step both ways, with pulse pressure.
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Every category page now helps you pick
The category and collection pages used to be a list of calculators and little else. Each one now explains which tool answers which question, covers the thing people most often get wrong in that category (weighted grades, sample versus population, margin versus markup, why combined VA ratings are not addition), and answers the questions we get asked most. Sources are also now listed on the calculators whose figures come from the IRS, the VA, the CDC, NIST and others, so you can check the number against the body that publishes it.
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Faster repeat visits, bigger buttons, easier browsing
Pages now cache properly in your browser, so moving between calculators is close to instant instead of a fresh download every time. Buttons, example chips, and the helpful/not-helpful controls are larger on phones so they are harder to mis-tap. The Retirement and Veteran Tools collections are now linked from every page instead of only the homepage.
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Labelled diagrams on the geometry, stair and statistics calculators
Some things are easier to see than to read. Eleven calculators now open with a labelled diagram, using exactly the same letters as the formula on the page: a, b and c for the triangle's sides, r and h for the round shapes, rise and run for a staircase, and the bell curve with its mean and standard deviations for the statistics tools. The cone diagram shows the difference between its height and its slant height, which is the most common reason a cone answer comes out wrong. The bell curves are drawn from the actual normal distribution rather than sketched, so the shaded areas really are the probabilities they claim: the middle band is 68.27 percent, and the two tails beyond 1.96 come to exactly 5 percent.
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Corrected what actually constrains a Google Ad Grant
The nonprofit signup value calculator used to explain the Ad Grant the way nearly every guide still does: as a $2 maximum cost per click you have to escape. Checking Google's own documentation while adding sources, that cap is no longer stated anywhere in it, and the manual bidding it applied to is not permitted for any Ad Grants account opened since April 2019. So the page now leads with the rule that is actually in force: conversion-based Smart Bidding is required on every campaign, only four strategies are allowed, and two of the four bid on value rather than volume. That is a better reason to put a number on a newsletter signup than a cap you cannot sit under anyway.
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Sources added to the last six calculators, and the S&P 500 table re-checked year by year
Six more calculators now list where their numbers come from, which finishes the job: 50 calculators cite a published source. The overtime rules on the time card, shift and work hours calculators point to the Department of Labor fact sheet that sets them, including the rule that hours cannot be averaged across two weeks, which is why overtime is figured per week here. The two email signup value calculators point to Google's own Ad Grants and conversion tracking policies and to the Fundraising Effectiveness Project. The S&P 500 calculator now names its dataset, and while adding the link we re-checked all 46 annual returns from 1980 through 2025 against it. Every year matched, including 2025 at 17.78 percent.
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New: Medicare IRMAA Calculator
Find your 2026 Medicare IRMAA surcharge from your 2024 income: Part B and Part D costs by tier, plus what the nearest bracket cliff is costing or would cost.
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New: Customer Lifetime Value Calculator
Free customer lifetime value calculator: enter order value, purchase frequency, margin, and retention to get discounted LTV, customer lifespan, and LTV to CAC.
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New: 401k Catch-Up Calculator
Find your 2026 401k catch-up: the age 50+ and 60-63 super limits, whether the new $150,000 Roth rule applies to you, and what the catch-up years are worth.
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New: Social Security COLA Calculator
Apply the 2026 COLA of 2.8% to your benefit and see the honest version: the net check after the Medicare Part B increase, and the share of your raise it ate.
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New category: Business and Marketing
Advertising and unit economics tools now have their own home, starting with customer lifetime value, the value of an email signup for businesses and for nonprofits, and Amazon FBA profit. More is on the way: invoicing, markup versus margin, break even, and mileage.
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New: Email Signup Value Calculator
Work out what one email or newsletter signup is worth, so you can assign a real conversion value in Google Ads, GA4, and Performance Max instead of guessing.
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New: ROAS Calculator
Free ROAS calculator: revenue and ad spend give your return on ad spend, and your margin gives the break-even ROAS that decides if it is actually profit.
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New: 529 Calculator
Project your 529 balance to the first day of college, escalate costs at real college inflation, and see which years it covers, with the Roth rollover priced.
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New: Estate Tax Calculator
Check your estate against the 2026 federal exemption of $15 million per person, see the tax on any excess, and price the portability election most people skip.
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New: Nonprofit Email Signup Value Calculator
Calculate what a newsletter signup is worth to your nonprofit, using donor lifetime value and real retention rates, so Google Ads and Ad Grants can bid on it.
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New: Inherited IRA RMD Calculator
Work out your inherited IRA RMD under the 10-year rule: this year's required minimum, your deadline, and the year-10 tax bomb that minimums quietly build.
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New: Break-Even Calculator
Free break-even calculator: fixed costs and contribution margin give break-even in units and revenue, plus profit targets and your margin of safety.
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New: CPA Calculator
Free CPA calculator: ad spend and conversions give your cost per acquisition, and the conversion's value gives the max affordable CPA you can pay and profit.
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New: CD Ladder Calculator
Build a CD ladder from your real quoted rates and race it against all-in long CDs and rolling short ones: ten-year values, yearly maturities, and the price.
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New: Mileage Reimbursement Calculator
Calculate mileage reimbursement with the 2026 IRS rates, including the July increase to 76 cents, split-year totals, parking and tolls, and taxable excess.
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New: Cart Abandonment Calculator
Free cart abandonment calculator: your rate against the 70% average, the honest recoverable revenue from emails, and what one point of improvement is worth.
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New: Margin Calculator
Free margin calculator: revenue and costs give your gross, operating, and net margins as one readable ladder, plus the right price for any target margin.
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New: Markup vs Margin Calculator
Free markup vs margin calculator: enter cost and price, or price for a target margin, and see both percentages side by side so the mix-up never costs you.
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New: Loot Drop Calculator
Turn any drop rate into honest odds: your chance within the runs you plan, the attempts needed for 90% and 99% confidence, and why nothing is ever due.
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New: Invoice Calculator
Free invoice calculator: add line items, apply a discount and sales tax in the right order, subtract the deposit, and get the balance due with the due date.
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New: Markup Calculator
Free markup calculator: turn a cost and markup into a price, a price into its markup, or a shelf price into the cost beneath it, with chained markups solved.
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New: I Bond Calculator
Build the I-bond composite rate from Treasury's own formula, project your bond's growth with the penalty priced, and race it against a CD after state tax.
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New: MTG Opening Hand Calculator
Exact hypergeometric odds for your MTG deck: at least one copy in the opener, the full exactly-k spread, play vs draw by any turn, and London mulligans.
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New: Email Revenue Calculator
Free email revenue calculator: revenue per delivered email against the 10 cent benchmark, per campaign, per subscriber per year, and your honest email ROI.
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Cooking and Kitchen plus Unit Conversions categories
Two new categories went live. Cooking and Kitchen has cups to grams by real ingredient density, butter and oven conversions, recipe scaling, and pan sizes. Unit Conversions covers millimeters to inches, kilograms to pounds, milliliters to ounces, and more, each with the exact factor and a worked example.
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An updates log and a how we verify page
We started publishing this log so you can see when calculators launch, when the numbers behind them get refreshed, and what changed. The new how we verify page explains how we check that the math is right.
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Dark mode arrived
Calcaholic now follows your device light or dark setting automatically, with a manual toggle in the header that remembers your choice.
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Freshness stamps on data driven calculators
Calculators whose answers depend on published figures (tax brackets, VA rates, contribution limits, cost averages, API prices) now show when we last reviewed that data. Timeless math like fractions and derivatives gets no stamp, because a review date on arithmetic would be noise pretending to be diligence.
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Cite and feedback tools on every calculator
You can now copy an APA, MLA, or plain citation for any calculator, and tell us with a thumbs up or thumbs down whether a tool actually helped.
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Four more math calculators
Added long division with the steps narrated a digit at a time, a rounding calculator that gets the 1.005 case right where floating point usually gets it wrong, combinations and permutations, and scientific notation.
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Corrected the derivative calculator description
It said the tool handled any function. It now names what it actually supports: polynomials, trigonometric, exponential, and logarithmic functions. An overpromise is a bug.
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Shift and work hours calculators
Two new payroll tools, each with an honest note on overtime: the federal rule is weekly over 40, and only some states add a daily rule on top of it.
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Time and date calculators
Added a time duration calculator, a road trip planner, and an upgraded time card with per week overtime and a print button.
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Derivative calculator: graphs, tangent lines, and check my answer
The derivative calculator now graphs a function beside its derivative, draws the tangent line at a chosen point, handles fourth and fifth derivatives, and can check your own answer for equivalence and tell you which mistake you probably made.
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Step by step derivative calculator
A full symbolic differentiation engine that shows every rule it applies, free, with graphs, higher order derivatives, and a check my answer tool.
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Math pages now show their work
Math, statistics, and geometry calculators walk through the steps using the numbers you actually entered, not just a canned example. The steps come from the same code that produces the answer, so the two can never disagree.
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Geometry, probability, and roots
Added circle, triangle, and right triangle solvers, sphere, cylinder, and cone volumes, a dice roller, a random number generator, square roots in simplified radical form, GCF and LCM, and a probability calculator.
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2026 Roth IRA contribution limits
Updated to the IRS figures for the 2026 tax year: $7,500, or $8,600 if you are age 50 or older, which is a catch-up of $1,100.
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Calcaholic went live
The site launched with our first wave of fast, free, no clutter calculators across grades, math, statistics, finance, and health.