Random Number Generator
Generate any amount of random numbers in a range, as integers or decimals, with an option to keep every value unique.
Example
Generate 5 unique integers between 1 and 100:
Min: 1 Max: 100 Count: 5
Type: Integer Unique: On
Result: 42, 7, 88, 19, 63
Count 5 · Sum 219 · Min 7 · Max 88 · Mean 43.8
Each draw uses rejection sampling on crypto.getRandomValues so every integer in the range is equally likely (no modulo bias).
How it works
Set the minimum, maximum and how many numbers you want, pick integer or decimal mode, then press Generate. Each value is drawn from crypto.getRandomValues for cryptographically strong randomness.
Good to know
CalcCafe's Random Number Generator draws random whole numbers or decimals between a minimum and maximum you set, in any quantity you specify, with an optional switch to force every value to be distinct. It is built for anyone who needs unpredictable numbers without a spreadsheet formula or coding: running a raffle or giveaway, picking lottery-style numbers, sampling rows from a dataset, assigning random IDs, seeding a game or quiz, or stress-testing something with arbitrary input.
Reach for it whenever you want fairness you can defend. Because it draws from the browser's cryptographic random source rather than a seedable pseudo-random generator, the output cannot be predicted or reproduced by guessing a seed, which matters when the result decides a prize, an order, or a selection people might dispute. The unique-values option is the one to enable for draws where the same number must not appear twice, such as choosing distinct winners or bingo balls.
The main output line lists your numbers in draw order, separated by commas, and the summary tiles below report the count actually produced, the sum, the lowest and highest values drawn, and the mean. Use those stats as a quick sanity check: if the count is lower than you asked for, or the message turns into a warning, the generator is telling you the range was too narrow to satisfy your settings.
- Unique integers are capped at the number of whole values in the range (1 to 10 yields at most 10), and unique decimals depend on the decimal-places setting, so widen the range or add decimal places if it refuses to fill your count.
Frequently asked questions
How is this different from Math.random()?
It uses crypto.getRandomValues, the browser's cryptographically strong random source, with rejection sampling for integers so the values are unbiased and unpredictable rather than from a seedable pseudo-random generator.
Why does 'Unique values' sometimes refuse to generate?
Unique mode cannot produce more values than the range allows. For integers from 1 to 10 you can get at most 10 unique numbers; for decimals, increase the decimal places or widen the range to create more distinct possibilities.
Is my data uploaded anywhere?
No — this calculator runs entirely in your browser; nothing is uploaded.
Is it free?
Yes, completely free with no sign-up and no limits.
People also ask
Is a random number generator truly random?
This tool uses the browser's crypto.getRandomValues, which is a cryptographically strong source designed to be unpredictable, and applies rejection sampling so each integer is equally likely. It is far stronger than ordinary seedable pseudo-random functions, though no software generator is provably random in a philosophical sense.
How do I pick random lottery numbers with it?
Set the minimum and maximum to your lottery's number range, set how many numbers to draw, choose Integer, and turn Unique values on so no number repeats. Press Generate to get a distinct set within the range.
Can it generate numbers without repeats?
Yes. Turn on the Unique values option and every number in the output will be distinct, as long as the range is wide enough to hold the count you requested.
What is the difference between integer and decimal mode?
Integer mode returns whole numbers only, while decimal mode returns fractional numbers rounded to the number of decimal places you choose (0 to 10). Decimal mode gives far more possible distinct values within the same range.
How many random numbers can I generate at once?
You can request large batches; the tool caps a single generation at 100,000 numbers. For unique values the practical limit is also bounded by how many distinct numbers fit in your chosen range.
Is this random number generator free and private?
Yes. It runs entirely in your browser with no sign-up and no limits, and none of your inputs or results are uploaded anywhere.
Why are my random numbers different every time I click Generate?
Each click draws a fresh set from the cryptographic random source, which is not seeded, so results are not reproducible by design. If you need a fixed list, copy the output before generating again.
What does the mean shown in the results mean?
The mean is the average of the numbers just generated, calculated as the sum divided by the count. With truly random draws over a range, the mean tends toward the middle of that range as you generate more numbers.
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