Dice Probability Calculator

Pick how many dice, how many sides and a target. The calculator works out the exact chance of hitting that total or more, and charts every possible result.

How the math works

A single fair die gives every face the same chance, so a d6 has a 1 in 6 chance for each number. Add more dice and the totals bunch toward the middle, because there are more ways to make 7 on 2d6 (six ways) than to make 2 (one way). The calculator counts every combination exactly instead of simulating rolls, so the numbers do not drift.

Using it at the table

For damage, set the dice and modifier to see your average and the chance of dropping a creature with a known number of hit points. For d20 tests, subtract your modifier from the DC to get the number you need on the die, then read the table above. Each step on a d20 is worth 5%.

Advantage and disadvantage odds

With advantage, the chance of success is 1 minus the chance that both dice miss. With disadvantage, both dice have to succeed, so you square the single die chance. Needing a 15, for example, is 30% on one die, 51% with advantage and 9% with disadvantage.