About the Dice Roller
This online dice roller replaces a missing set of dice for board games, tabletop RPGs like Dungeons & Dragons, classroom probability lessons and quick party games. Choose how many dice to roll and how many sides they have — d4, d6, d8, d10, d12, d20 or d100 — add a modifier, and you get every individual die plus the total.
Tabletop players can type standard dice notation instead: 1d20+5 for an attack roll, 8d6 for a fireball, 2d8+1d6+3 for a mixed damage roll, or d% for a percentile check. The roller shows the lowest and highest possible totals, the average you should expect, and — when you set a target — the exact chance of meeting or beating it (for example a DC 15 saving throw).
Each die uses a cryptographically secure random number, so every face is equally likely and rolls are independent. The chart shows the full probability distribution of the total, which makes it easy to see why 7 is the most common roll on 2d6 and why rolling more dice makes results cluster around the middle.
With the default inputs, the total is 12. Change any value above to recalculate instantly.
How to use the dice roller
- 1Choose how many dice to roll and how many sides each die has.
- 2Add a modifier if your game adds or subtracts a bonus.
- 3Or type dice notation such as 1d20+5 or 2d8+1d6+3 to roll mixed dice.
- 4Optionally enter a target number to see your chance of meeting or beating it.
- 5Change any input to roll again; add a seed if you need a repeatable roll.
Formula and method
Each die is a random whole number from 1 to S, each face equally likely. The average of one die is (S + 1) ÷ 2 (3.5 for a d6, 10.5 for a d20) and its variance is (S² − 1) ÷ 12. For several dice these add up, and the modifier shifts the whole range without changing the spread.
The exact probability of every total is found by convolving the single-die distributions one die at a time. The chance of hitting a target is the sum of the probabilities of all totals at or above it. For very large pools (hundreds of dice) the tool switches to a normal approximation with a continuity correction for the target odds and the chart.
- N
- Number of dice
- S
- Sides per die
- M
- Flat modifier added to the total
- σ
- Standard deviation of the total
Worked examples
Two standard dice (2d6)
Two six-sided dice total between 2 and 12, averaging 7. Of the 36 equally likely outcomes, 21 total 7 or more, so the chance of rolling at least 7 is 21 ÷ 36 ≈ 58.3%.
D&D attack roll: 1d20+5 against AC 15
A d20 plus 5 ranges from 6 to 25 with an average of 15.5. To reach 15 you need a natural 10 or higher — 11 of 20 faces — so the hit chance is 55%.
Fireball damage: 8d6
Eight d6 average 8 × 3.5 = 28 damage with a standard deviation of about 4.83. Totals of 35 or more are uncommon: counting all 1,679,616 outcomes gives about a 9.07% chance.
Frequently asked questions
What does 2d6+3 mean?+
It means roll two six-sided dice, add the faces together and then add 3. The result ranges from 5 to 15 and averages 10. The first number is how many dice, the number after “d” is the sides.
What is the most common roll with two dice?+
Seven. Six of the 36 combinations total 7 (1+6, 2+5, 3+4 and their reverses), a 16.7% chance, while 2 and 12 each have only one combination, a 2.8% chance.
Is this dice roller truly random?+
Each die uses the browser’s cryptographically secure random generator, so every face has exactly the same chance and each roll is independent. Physical dice can be slightly biased by manufacturing flaws.
How do I roll a d100 or percentile dice?+
Choose d100 from the sides menu or type d% or 1d100 in the notation box. The result is a whole number from 1 to 100, each with a 1% chance.
How do I roll with advantage in D&D?+
Roll 2d20 and keep the higher die. The chance of rolling at least a 15 rises from 30% on one d20 to 51% with advantage, because you only fail if both dice are 14 or lower.
Can I mix different dice in one roll?+
Yes. Type something like 2d8+1d6+3 or 1d12-1d4 in the notation box. The tool rolls each group, shows every die, and calculates the combined range, average and odds.