How the grade calculator works
Most classes don't treat every assignment equally — a midterm worth 25% of your grade matters five times more than a quiz worth 5%. Your course grade is therefore a weighted average: each score is multiplied by its weight before averaging. This calculator does that for every row you fill in and skips the blank ones, so it works just as well three weeks into the semester as it does at the end.
The weights don't have to add up to 100. If only 50% of your course has been graded so far, enter just those items — the calculator divides by the total weight you entered, which gives your true standing on the work graded to date.
The formula
Each grade is an assignment score in percent, each weight is how much that assignment counts (percent of the course, or raw points — anything proportional works), and Σ means "sum over all the assignments you entered."
Worked example
Suppose you've been graded on three things so far: an Essay at 91% (weight 15), a Midterm at 84% (weight 25), and a Lab at 95% (weight 10):
Grade = (91×15 + 84×25 + 95×10) ÷ (15 + 25 + 10) = (1,365 + 2,100 + 950) ÷ 50 = 4,415 ÷ 50 = 88.3%
On the standard letter scale that's a B+ — and notice it sits closer to the midterm's 84 than to the lab's 95, because the midterm carries most of the weight.
The letter grade scale (and why yours might differ)
This calculator uses the common plus/minus scale: A 93+, A− 90–92.9, B+ 87–89.9, B 83–86.9, B− 80–82.9, C+ 77–79.9, C 73–76.9, C− 70–72.9, D+ 67–69.9, D 63–66.9, D− 60–62.9, and F below 60. But grading scales are set by schools (and sometimes individual instructors), and they genuinely vary — plenty of schools use a straight 10-point scale with no plus/minus, and some set the A bar at 90 or even 94. Treat the letter here as a strong estimate, and check your syllabus for the scale that actually applies to you.