Random Number Generator
Generate random integers or decimals within a range, with uniform or normal (Gaussian) distribution, and optional unique values.
How to Use
- Set the minimum and maximum values for the range.
- Choose "Integer" or "Decimal" and set decimal places if needed.
- Set how many numbers to generate (1–1000).
- Choose "Uniform" (every value equally likely) or "Normal" (values cluster around the middle, bell-curve distribution).
- Enable "Unique values only" to avoid repeats (only available for integers, when the range is large enough).
- Click Generate — copy individual values or all at once.
When to Use This
- Drawing raffle or lottery numbers for an informal prize, where unique values stops the same ticket being picked twice in one round.
- Generating a sample of plausible latencies or test scores on the normal setting, so a chart or statistics exercise shows a bell curve instead of a flat band.
- Choosing which spreadsheet rows to spot-check, by generating a unique set of row numbers between 1 and the length of the sheet.
- Assigning people to groups or a running order, when you want an impartial answer and nobody wants to argue about who decided it.
Frequently Asked Questions
About This Tool
Two distributions cover most needs. A uniform draw gives every value in the range the same chance, as sampling and a fair die require. A normal draw clusters values around a mean with a spread set by the standard deviation, which is how measured quantities such as response times or heights behave. The Box-Muller transform turns two uniform values into a normally distributed one, by way of a square root of a logarithm and a cosine.
Set a minimum and a maximum; values out of order are swapped for you. Integer mode rounds the draw, decimal mode rounds to between 0 and 10 places, and the count runs from 1 to 1000. Normal mode centers the curve on the midpoint and sets the standard deviation to one sixth of the range, so it spans about six deviations. Unique values, for integers only, draws until the set is full, then shuffles.
Notes & Limits
- Integers come from rounding a continuous draw, so the two endpoints are produced about half as often as the values between them. For an exactly uniform integer range that is a real bias.
- Normal mode clamps anything outside the range back to the boundary, piling roughly a tenth of a percent of draws onto each endpoint. The result is not a true truncated normal.
- With unique values on, the tool keeps drawing until it has enough distinct ones. Requesting a count close to the size of the range, especially on normal, makes that loop slow.
- Decimal places go to ten, but double-precision arithmetic carries only about 15 to 17 significant digits, so across a wide range the last places shown are rounding artifacts.