Whether you are short a twenty-sided die for game night or need to roll forty dice at once, this roller handles it: pick the die type, the number of dice and any modifier, and roll. The result shows each die, the total, the possible range and — for standard rolls — the exact probability of what you got.
How to use the dice roller
- Enter the number of dice (1–100).
- Choose the type of die: d4, d6, d8, d10, d12, d20, d100, or a custom number of sides up to 1,000.
- Add a modifier if the roll has a bonus or penalty, such as +3 or −1.
- Choose whether to keep all dice or drop the lowest or highest one.
- Press Roll. The tape shows the notation (for example 4d6 drop lowest), each die, the total and the range.
When all dice are kept, the tape also gives the chance of rolling exactly your total and the chance of rolling at least that much.
Dice math
For N dice with S sides each, plus a modifier M:
Each die is uniform, but their sum is not: middle totals can be made in more ways, so they come up more often. The roller computes the exact distribution by convolution — combining the dice one at a time — rather than by approximation.
Two six-sided dice
| Total | Ways | Probability |
|---|---|---|
| 2 or 12 | 1 | 2.78% |
| 3 or 11 | 2 | 5.56% |
| 4 or 10 | 3 | 8.33% |
| 5 or 9 | 4 | 11.11% |
| 6 or 8 | 5 | 13.89% |
| 7 | 6 | 16.67% |
All 36 combinations of two dice are equally likely; 7 is most common because six of them add to 7.
Worked example: an ability score roll
Roll 4d6, drop the lowest. Suppose the dice show 5, 1, 4 and 3.
- The lowest die, 1, is dropped (the tape shows it in parentheses and fades it).
- The total is 5 + 4 + 3 = 12.
- The kept total can range from 3 to 18. Its long-run average is about 12.24 — higher than the 10.5 average of a plain 3d6, because dropping the worst die removes low results.
Advantage, disadvantage and other tricks
- Advantage: 2d20, drop the lowest. Average 13.825; chance of a 20 is 1 − (19/20)² = 9.75%.
- Disadvantage: 2d20, drop the highest. Average 7.175; chance of a 20 is (1/20)² = 0.25%.
- Percentile roll: 1d100 gives each value from 1 to 100 a 1% chance.
- Damage with a bonus: 2d8+3 ranges from 5 to 19 and averages 12.
- Coin as a die: a custom 2-sided die works like a coin flip, though the coin flipper keeps streak statistics.
Common dice at a glance
| Die | Faces | Average roll | Chance of max |
|---|---|---|---|
| d4 | 4 | 2.5 | 25% |
| d6 | 6 | 3.5 | 16.67% |
| d8 | 8 | 4.5 | 12.5% |
| d10 | 10 | 5.5 | 10% |
| d12 | 12 | 6.5 | 8.33% |
| d20 | 20 | 10.5 | 5% |
| d100 | 100 | 50.5 | 1% |
Rolling many dice makes the total look more and more like a bell curve — the normal distribution calculator approximates large rolls well. For a single number in a range, use the random number generator.
Every die is rolled with cryptographic randomness in your browser. Dice have no memory: a run of low rolls says nothing about the next one.
Frequently asked questions
How do I roll with advantage or disadvantage?
Roll 2 d20 and choose Drop the lowest die for advantage, or Drop the highest die for disadvantage. Advantage raises the average from 10.5 to 13.825 and the chance of a natural 20 from 5% to 9.75%.
What does 3d6+2 mean?
Roll three six-sided dice, add them up, then add 2. The result ranges from 5 to 20 and averages 12.5.
Are the dice fair?
Yes. Each die uses your browser's cryptographic random generator with rejection sampling, so every face is exactly equally likely. Physical dice can be slightly biased by uneven edges or air bubbles.
What is the most common total with two dice?
Seven. Six of the 36 equally likely combinations add to 7, a probability of 1 in 6. Totals of 2 and 12 each have just one combination (1 in 36).
What is the average for 4d6 drop the lowest?
About 12.24, compared with 10.5 for a plain 3d6. Dropping the lowest of four dice is a common way to generate character ability scores.