How this dice roller works
Every click of Roll asks your browser for fresh random numbers, one per die, and maps each one to a face with equal probability. A d6 gives each of its six faces exactly a 1 in 6 chance; a d20 gives each face 1 in 20. The dice you see are drawn as clean SVG shapes (pips for the d6, numerals for the rest), the total and each individual value appear instantly, and your last 10 rolls stack up in a session history along with a running average you can check against the theoretical one. In dice notation, the settings above read as count, then d, then faces: 2 dice of type d6 is the classic 2d6, and 1d20 is the single twenty-sider that decides so many tabletop fates.
Is it fair? What pseudorandom honestly means
The rolls come from your browser's built-in generator (Math.random), which is a pseudorandom generator: a deterministic formula that produces a sequence of numbers that passes statistical tests for uniformity. Nobody at your table can see its internal state or predict the next roll, and over thousands of rolls each face comes up as often as it should, so for games it behaves exactly like a fair die. What it is not is cryptographically secure: given enough consecutive outputs and serious effort, a mathematician could in principle reconstruct the sequence. That matters for lotteries and passwords, not for whether your barbarian hits the goblin. If you want numbers for something beyond games, our random number generator covers that ground in more depth.
The 2d6 table every board gamer should know
Roll two six-sided dice and the totals are not equally likely, because there are 36 equally likely combinations but different totals claim different numbers of them. Seven is king with 6 of the 36 ways. This is the math underneath craps, Catan, and Monopoly:
| Total | Ways out of 36 | Probability |
|---|---|---|
| 2 | 1 | 2.8% |
| 3 | 2 | 5.6% |
| 4 | 3 | 8.3% |
| 5 | 4 | 11.1% |
| 6 | 5 | 13.9% |
| 7 | 6 | 16.7% |
| 8 | 5 | 13.9% |
| 9 | 4 | 11.1% |
| 10 | 3 | 8.3% |
| 11 | 2 | 5.6% |
| 12 | 1 | 2.8% |
That is why the 6 and 8 hexes in Catan are prime real estate and why the robber lives on 7. If you want to compute odds for other dice combinations or events, our probability calculator does the general case.
Dice notation in 30 seconds
The shorthand you see in rulebooks is count, the letter d, then faces: 3d8 means roll three eight-sided dice and add them up. Modifiers tack on at the end, so 2d6+3 means roll 2d6 and add 3 to the total. One quirk worth knowing: adding dice does not just raise the average, it reshapes the odds. A single d12 lands on any face with equal probability, a flat line from 1 to 12. Roll 2d6 instead (same maximum, similar average) and the results hump up in the middle: you will see totals of 6, 7, and 8 constantly and a 2 or 12 only once in 36 rolls. Game designers pick between flat and humped distributions on purpose, and now you can too. For more dice-adjacent probability in playable form, try our penalty shootout simulator, which is the same honest randomness wearing football boots.