Generate a random whole number from 1 to 20, for a twenty-sided die (d20), the main die in Dungeons & Dragons.
Press Generate for a random number between 1 and 20. Both ends are included and each of the 20 numbers has exactly a 1 in 20 chance.
Odds for numbers between 1 and 20
Possible numbers
20
Chance of any one number
1 in 20 (5.0%)
Chance of repeating the last number
1 in 20
Chance a given number appears at least once in 20 picks
64.2%
Average result over many picks
10.5
Even / odd numbers
10 even, 10 odd
The last-but-one row surprises many people: even with 20 picks, a particular number has a 35.8% chance of never coming up, because picks are independent.
What a 1–20 range is used for
A random number between 1 and 20 is handy for a twenty-sided die (d20), the main die in Dungeons & Dragons.
What are the odds of getting a specific number between 1 and 20?
Each number has a 1 in 20 chance (5.0%) on every pick.
Can the same number come up twice in a row?
Yes, if repeats are allowed: the chance of repeating the previous number is 1 in 20. Tick "No repeats" when picking several numbers to get all-different results.
Are 1 and 20 included?
Yes. Both ends are included, so there are 20 possible numbers.