Dice Roller

Choose how many dice to roll, how many sides they have and any modifier, then press Roll the dice. Rolls use your browser’s cryptographically secure random number generator, so every face is equally likely. You see each die, the total, the range of possible totals and the average.

Useful when the real dice have gone missing: board games, tabletop role-playing games, classroom probability lessons, or deciding who goes first. It handles up to 20 dice of D4, D6, D8, D10, D12, D20 or D100, which covers standard dice notation such as 3d6, 2d8+1 or 1d20−2.

How the roller makes each roll fair

Each die is rolled independently with crypto.getRandomValues, a random source designed for security uses. A naive “random number modulo 6” introduces a tiny bias towards low numbers, so the roller discards the few raw values that would cause it (rejection sampling). The result is an exactly uniform choice between 1 and the number of sides, with no pattern and no memory of earlier rolls.

Reading dice notation

• 1d20 — one twenty-sided die.
• 3d6 — three six-sided dice, added together (3 to 18).
• 2d8+3 — two eight-sided dice, plus 3 (5 to 19).
• 1d100 or d% — a percentile roll from 1 to 100.

Two dice: the odds of every total

Every total of two six-sided dice, from all 36 equally likely combinations.

Total	Ways to roll it	Probability	Percent	Chance of this or higher
2	1	1/36	2.78%	100.00%
3	2	2/36	5.56%	97.22%
4	3	3/36	8.33%	91.67%
5	4	4/36	11.11%	83.33%
6	5	5/36	13.89%	72.22%
7	6	6/36	16.67%	58.33%
8	5	5/36	13.89%	41.67%
9	4	4/36	11.11%	27.78%
10	3	3/36	8.33%	16.67%
11	2	2/36	5.56%	8.33%
12	1	1/36	2.78%	2.78%

Adding dice makes the middle totals more likely, because there are more combinations that reach them. One die gives a flat distribution; two give a triangle peaking at 7; three or more start to look like a bell curve. That is why 3d6 rarely rolls 3 or 18 (each 1 in 216) but often lands between 9 and 12.

Standard dice

The standard polyhedral dice: range, average roll and the chance of rolling the highest face.

Die	Range	Average roll	Chance of the top face
d4	1–4	2.5	25.00%
d6	1–6	3.5	16.67%
d8	1–8	4.5	12.50%
d10	1–10	5.5	10.00%
d12	1–12	6.5	8.33%
d20	1–20	10.5	5.00%
d100	1–100	50.5	1.00%

Using the roller to teach probability

Roll 2d6 thirty or forty times and tally the totals, then compare your tally with the table above. Small samples wander a long way from the expected percentages; larger ones settle towards them. It is a quick, concrete demonstration of the law of large numbers, and the exact probabilities are a simple percentage of 36.

Frequently asked questions

Is this online dice roller fair?

Yes. Each roll uses your browser’s cryptographically secure random number generator (crypto.getRandomValues), the same source used for security keys, with rejection sampling so every face is exactly equally likely. Nothing is predetermined or sent to a server.

What does 2d6 or 1d20+3 mean?

The number before the d is how many dice to roll, the number after it is how many sides each has, and any +/− number is a modifier added to the total. 2d6 is two six-sided dice; 1d20+3 is one twenty-sided die plus 3.

What is the most likely total with two dice?

7. Six of the 36 equally likely combinations add up to 7 (1+6, 2+5, 3+4, 4+3, 5+2, 6+1), a probability of 16.67%. Totals of 2 and 12 are the least likely, at 1 in 36 each.

What is the average roll of a die?

For a die with s sides it is (s + 1) ÷ 2: 3.5 for a d6, 10.5 for a d20. For several dice, multiply by the number of dice and add any modifier.

How do I roll a d100 (percentile dice)?

Choose D100 and roll one die. The result is 1 to 100 with equal chances. With physical dice this is often done with two ten-sided dice, one for tens and one for units, with 00 and 0 read as 100.

What are the odds of rolling a natural 20?

1 in 20, or 5%, on any single d20 roll. Rolling with advantage (two d20s, keep the higher) raises the chance of at least one 20 to 9.75%.