How to use the random number generator
- Choose Numbers, Dice or Coin flip.
- Set the range, the dice or the number of coins.
- Press Generate, Roll or Flip. Results are shown, read out by screen readers, and can be copied.
Random numbers
- The minimum and maximum are both included, and can be negative. If the minimum is larger, they are swapped.
- Generate up to 10,000 numbers at once, between −1,000,000,000,000,000 and 1,000,000,000,000,000.
- No repeats makes every number different, like a raffle or lottery draw.
- Decimal places picks from evenly spaced values: with 2 places, 0 to 1 gives 0.00, 0.01 … 1.00. The values are worked out exactly, without rounding errors.
Dice notation
Use the quick buttons for common dice, or type any combination:
| Notation | Meaning |
|---|---|
d20 | One twenty-sided die |
3d6+2 | Three six-sided dice, plus 2 |
2d20kh1 | Two d20s, keep the highest (advantage). kl1 keeps the lowest. |
4d6dl1 | Four d6s, drop the lowest. dh1 drops the highest. |
d% | A percentile die, the same as d100 |
1d8+1d6-1 | Mix dice and numbers with + and - |
Dropped dice are shown crossed out with the word “dropped”. Among equal dice, the earlier one is kept. Each roll shows the lowest and highest totals possible, and earlier rolls stay in the history until you reload the page.
How the randomness works
Every result comes from your browser’s cryptographically secure random number generator. Rejection sampling makes every outcome exactly equally likely, avoiding the slight bias of simpler methods. Nothing is sent anywhere or stored.
Limitations
- Up to 6 decimal places, and the range can hold at most about 9 quadrillion possible values.
- Up to 100 dice per group, 500 in total, with up to1,000 sides. Exploding and rerolling dice aren’t supported.
- Up to 100 coins at a time.
- To create passwords or secret keys, use the Password Generator, which is built for that.
Frequently asked questions
Are the numbers truly random?
They come from your browser’s cryptographically secure random number generator (crypto.getRandomValues), which is designed to be unpredictable. Each result is chosen with rejection sampling, so every number in the range, every face of a die and both sides of a coin are exactly equally likely.
How do I pick lottery numbers?
Set the minimum and maximum to the lottery’s range, choose how many numbers, and tick No repeats. For example, 6 numbers from 1 to 59 with Smallest first. Random picks are just as likely to win as any others: no method can predict a fair draw.
Why do I get the same number twice?
With repeats allowed, each number is drawn independently, so repeats happen naturally: drawing 10 numbers from 1 to 100 gives at least one repeat about 37% of the time. Tick No repeats if every number must be different.
What does 2d20kh1 mean?
Roll two twenty-sided dice and keep the highest one, which is “advantage” in Dungeons & Dragons. 2d20kl1 keeps the lowest, for disadvantage. 4d6dl1 rolls four six-sided dice and drops the lowest, a common way to roll character stats.