Select dice type and click Roll!
Standard RPG Dice Explained
A fair die gives every face the same chance, so a D6 lands on any given number 1 time in 6 (16.7%) and a D20 1 time in 20 (5%). With two D6 the most likely total is 7, at 6 chances in 36. Pick a die, a count and a modifier above and the roller adds it all up in standard notation such as 2d6+3.
Tabletop RPGs like Dungeons and Dragons use a standard set of seven polyhedral dice. Each die is named for its number of faces: D4 (tetrahedron), D6 (cube), D8 (octahedron), D10 (pentagonal trapezohedron), D12 (dodecahedron), D20 (icosahedron), plus a second D10 marked 00 to 90 for percentile (D100) rolls. A full set covers every situation in the game, from rolling to hit an enemy to determining spell damage to making skill checks.
D4: Dagger & Magic
D6: The Classic
D8: Longsword
D10: Percentile
D12: Greataxe
D20: The King
How Modifiers Work
In D&D and most RPGs, you rarely roll a die and take the raw result. You add a modifier based on your character's ability scores. A Strength modifier of +3 means every Strength-based attack or check adds 3 to the die result. This roller handles modifiers directly: enter the modifier value and it adds automatically to every roll.
Advantage and disadvantage are key mechanics in D&D 5e. With advantage, roll two D20s and take the higher result. With disadvantage, take the lower. Rolling with advantage increases your average D20 result from 10.5 to approximately 13.8. Use this roller by setting count to 2 and reading the individual results.
2d6 Totals and Their Odds
Two six-sided dice have 36 equally likely combinations. Totals in the middle can be made more ways, which is why 7 comes up most and 2 or 12 least.
| Total | Ways (of 36) | Chance | This total or higher |
|---|---|---|---|
| 2 | 1 | 2.78% | 100% |
| 3 | 2 | 5.56% | 97.2% |
| 4 | 3 | 8.33% | 91.7% |
| 5 | 4 | 11.11% | 83.3% |
| 6 | 5 | 13.89% | 72.2% |
| 7 | 6 | 16.67% | 58.3% |
| 8 | 5 | 13.89% | 41.7% |
| 9 | 4 | 11.11% | 27.8% |
| 10 | 3 | 8.33% | 16.7% |
| 11 | 2 | 5.56% | 8.3% |
| 12 | 1 | 2.78% | 2.8% |
Doubles of any kind come up 1 time in 6 (16.67%). Snake eyes (two 1s) is 1 in 36.
D20 Target Numbers with Advantage
Chance of rolling at least the target on the die itself, before modifiers. For advantage, roll 2 dice above and keep the higher; for disadvantage, keep the lower.
| Need | Normal | Advantage | Disadvantage |
|---|---|---|---|
| 5 or more | 80% | 96.0% | 64.0% |
| 8 or more | 65% | 87.8% | 42.3% |
| 10 or more | 55% | 79.8% | 30.3% |
| 12 or more | 45% | 69.8% | 20.3% |
| 15 or more | 30% | 51.0% | 9.0% |
| 18 or more | 15% | 27.8% | 2.3% |
| Natural 20 | 5% | 9.8% | 0.3% |
Advantage lifts the average D20 roll from 10.5 to 13.825; disadvantage drops it to 7.175. The gain is biggest for middling targets around 10 to 11.
Average Rolls for Common Dice
The average of one die is (sides + 1) ÷ 2, and averages simply add, so 8d6 averages 8 × 3.5 = 28.
| Roll | Minimum | Maximum | Average |
|---|---|---|---|
| 1d4 | 1 | 4 | 2.5 |
| 1d6 | 1 | 6 | 3.5 |
| 2d6 | 2 | 12 | 7 |
| 3d6 | 3 | 18 | 10.5 |
| 2d8 | 2 | 16 | 9 |
| 1d12 | 1 | 12 | 6.5 |
| 1d20 | 1 | 20 | 10.5 |
| 8d6 (Fireball) | 8 | 48 | 28 |
| 4d6 drop lowest | 3 | 18 | 12.24 |
With 4d6 drop lowest, an 18 comes up about 1.6% of the time and 15 or more about 23.1%. The chance of at least one 6 in four rolls of a D6 is 51.8%, just better than even.
How the Roller Picks a Number
Each die is Math.floor(Math.random() × sides) + 1, which gives every whole number from 1 to the number of sides the same chance. Math.random is the browser's built-in pseudorandom generator: fair enough for tabletop games, board games and classroom probability, but not cryptographic, so it is not the right tool for gambling or anything with money at stake. For a probability you want to work out rather than roll, try the probability calculator.