How to roll dice online
The roller opens set to 2 dice with 6 sides, so you can roll a pair right away. Tap a preset to change the die type, or type any side count from 2 to 1,000. The modifier is added once to the total, never to each die.
Each press of Roll dice gives a fresh, independent result. Recent rolls stay in a history list for this page visit, and you can copy the result or download it as a PDF.
- Set the number of dice (1 to 100).
- Pick a preset like D6 or D20, or enter your own number of sides.
- Add a positive or negative modifier if your game uses one.
- Choose normal, keep higher or keep lower.
- Set the success threshold if you count dice at or above a target, then press Roll dice.
2 dice roller probability table
Two six-sided dice have 6 x 6 = 36 equally likely outcomes. Totals in the middle can be made in more ways, which is why 7 comes up most and 2 or 12 come up least. The last column is handy for games that ask you to beat a number.
This table is exact math for fair dice. Any short run of real rolls will wander from it, and that's normal.
| Total | Ways to roll it | Chance of exactly this | Chance of this or higher |
|---|---|---|---|
| 2 | 1 of 36 | 2.78% | 100% |
| 3 | 2 of 36 | 5.56% | 97.22% |
| 4 | 3 of 36 | 8.33% | 91.67% |
| 5 | 4 of 36 | 11.11% | 83.33% |
| 6 | 5 of 36 | 13.89% | 72.22% |
| 7 | 6 of 36 | 16.67% | 58.33% |
| 8 | 5 of 36 | 13.89% | 41.67% |
| 9 | 4 of 36 | 11.11% | 27.78% |
| 10 | 3 of 36 | 8.33% | 16.67% |
| 11 | 2 of 36 | 5.56% | 8.33% |
| 12 | 1 of 36 | 2.78% | 2.78% |
Reading dice notation like 2d6+3
The number before the d is how many dice to roll and the number after it is how many sides each die has. 2d6 means two six-sided dice. 2d6+3 means roll them, add the faces, then add 3 once. Its totals run from 5 to 15 and average 10.
The page shows simple NdS notation with a plus or minus modifier. It doesn't parse typed expressions or handle exploding dice, rerolls or drop-lowest rules like 4d6 drop 1.
Lowest total = N + modifierHighest total = N x S + modifierExpected total = N x (S + 1) / 2 + modifierStandard deviation = square root of (N x (S x S - 1) / 12)
D20 roller with keep higher and keep lower
For a single d20, set 1 die and 20 sides. Keep higher rolls the whole pool twice and keeps the larger total, and keep lower keeps the smaller. Both attempts stay on screen, and a tie keeps the first one. Some tabletop games call these advantage and disadvantage, but check your game's own rules for what they apply to.
Rolling twice changes the odds a lot. Needing 11 or higher on a d20 is a 50% chance normally, 75% with keep higher and 25% with keep lower.
| Target | Normal | Keep higher of 2 | Keep lower of 2 |
|---|---|---|---|
| 5 or higher | 80% | 96% | 64% |
| 10 or higher | 55% | 79.75% | 30.25% |
| 11 or higher | 50% | 75% | 25% |
| 15 or higher | 30% | 51% | 9% |
| 20 | 5% | 9.75% | 0.25% |
Counting successes in a dice pool
Some games count each die that meets a target instead of adding them up. Set the success threshold and every retained die at or above it counts as one success. The modifier changes the total only, not the successes.
With the default 2d6 and a threshold of 5, each die succeeds on a 5 or 6, a 33.33% chance. You'd expect 0.67 successes per roll on average, and the chance of at least one success is 55.56%.
Chance per die = (S - T + 1) / SChance of at least one success = 1 - (1 - chance per die)^N
Are online dice rolls fair?
Each face comes from crypto.getRandomValues(), the browser's cryptographically strong random source, not Math.random(). Values that would favor some faces over others are thrown out and redrawn (rejection sampling), so every face from 1 to S has the same chance.
That's fine for games and classroom use. It isn't a certified draw: there's no public seed or audit log, so don't use it for gambling, lotteries, prize drawings or anything where rules require witnessed or reproducible randomness.
Sources
These references cover the browser random source and the probability ideas behind the odds on this page.