Quick answer: Each whole number from 1 to 100 has the same chance, 1 in 100; drawing 5 without repeats picks 5 different numbers, each new seed giving a new set.
How it's calculated
A whole number from min to max is min + ⌊r × (max − min + 1)⌋, where r is a uniform random number from 0 up to (not including) 1, so every value in the range is equally likely. Decimals are min + r × (max − min), rounded to the places you choose.
With no repeats, a number that has already come up is drawn again, which is the same as pulling numbered balls from a bag without putting them back.
The numbers come from a seeded pseudo-random generator (mulberry32). The seed is any text: the same seed gives the same numbers, which is useful to repeat or check a draw, and a new seed gives a new draw. For security keys and official lotteries, use a certified cryptographic generator instead. For the chance of an outcome, see the probability calculator.
Worked examples
- Dice roll: min 1, max 6, 1 number → each face has probability 1/6
- Raffle with 250 tickets, 3 winners: min 1, max 250, 3 numbers, no repeats
- Number of possible draws of 5 from 100 (order ignored): C(100, 5) = 75,287,520
Frequently asked questions
Are the numbers truly random?
They are pseudo-random: produced by a formula that passes standard statistical tests and is fine for games, classroom picks and samples. They are not meant for passwords or regulated lotteries.
Why do I get the same numbers each time?
The draw depends on the seed. Change the seed text – any word or the current time – to get a new set.
How do I pick a random winner from a list of names?
Number the names from 1 to n, draw one number from 1 to n, and take that name.
Can I draw lottery-style numbers with no repeats?
Yes. Turn off repeats and set the count, say 6 numbers from 1 to 49, and no number will come up twice.
Can I use this for an official prize draw?
It's fine for a friendly draw. For a competition with legal rules, use a certified draw and keep a record, since anyone who has the seed can reproduce these numbers.
Can it give decimals?
Yes. Switch the type to decimals and choose how many places you want; 0 to 1 with two places gives numbers like 0.37 or 0.82.