Calculators
Random number maker and generator
This random number maker picks numbers between a minimum and a maximum that you choose. Use it as a random whole number generator, or switch to decimals with a set number of places. Ask for one number or a long list, allow repeats or turn them off, and copy the results. It runs in your browser.
How to use the random number generator
Choose Integers or Decimals under Number type. Type the lowest and highest values you want in Minimum value and Maximum value, then set How many numbers. The page opens on Integers, 1 to 100 and 10 numbers. In Decimals mode, Decimal places sets the precision, starting at 2.
Select No repeats if every number in the list must be different, then select Generate numbers. The results appear under Your numbers, one number per line, with a note that gives the count and says whether repeats were allowed.
Select Generate again for a fresh list. Changing any setting clears the last result, Cancel stops a run that is still going, and Reset puts every field back to its start value. Copy results puts the whole list on your clipboard. Download .txt saves it as random-numbers.txt, one number per line.
Whole numbers in any range
Both ends of the range are possible results, so a range holds the maximum minus the minimum, plus one, possible values. 1 to 6 holds 6, like a die, and -10 to 10 holds 21. Every value has the same chance on each draw: 1 in 6 for the die, 1 in 21 for the second range.
Negative numbers work with a hyphen or a minus sign, and a leading plus sign is accepted. When both ends are equal, every result is that number. Type digits only: 1,000 and 1e3 are rejected, and in Integers mode 2.5 gives an error that points you to Decimals.
There is no size limit on the range. The generator uses exact whole-number arithmetic, so 1 to 10 to the power 30 works, and values beyond 9,007,199,254,740,991 stay exact. A range of 1000 to 9999 gives 4-digit numbers. No leading zeros are added, so 0 to 9999 can give 42 but never 0042.
Random decimals
Set Number type to Decimals to get numbers with a fixed count of decimal places. The generator splits the range into even steps: at 2 places the step is 0.01, so 0 to 1 holds 101 possible values, from 0.00 to 1.00, each equally likely. At 3 places, 1 to 2 holds 1,001.
Results always show every decimal place, so you get 1.00 and 0.50 rather than 1 and 0.5. Negative decimals work too, such as -1 to 0. Each value is worked out with whole-number arithmetic on the steps, so no floating-point rounding creeps in.
An endpoint must fit the precision you chose. At 2 places, 0.125 gives an error instead of being rounded; raise Decimal places to 3 or change the endpoint. Zeros at the end do not count, so 1.50 is fine at 1 place. Write 0.5 rather than .5, because a value needs a digit before the point.
No repeats
With repeats allowed, each draw can land on any value in the range, so a list can hold the same number twice. Eleven draws from 1 to 10 always repeat at least one number. Select No repeats when every number must differ, such as 6 numbers from 1 to 49.
No repeats draws without replacement. Each value that is picked leaves the pool, and the next draw chooses evenly among the values left. How many numbers can then be at most the number of possible values, so asking for 11 numbers from 1 to 10 shows an error beside that field and no list.
Set How many numbers to the size of the range to get every value once in random order, such as 1 to 10 shuffled. The pool is tracked without writing out the whole range, so No repeats also works from 1 to 10 to the power 30. The rule holds inside one list; Generate again can repeat numbers from the last one.
How the numbers are chosen
The random source is Web Crypto, the browser's cryptographically secure random number generator, which the page reads through getRandomValues. Each draw takes just enough random bits to cover the range. For 1 to 6 that is 3 bits, a value from 0 to 7: values 0 to 5 become 1 to 6, and a 6 or 7 is thrown away and drawn again.
This is rejection sampling. The common shortcut keeps the remainder of a large random value after division, and it favors some numbers slightly whenever the range does not divide the random values evenly. Discarding the extra values gives every number exactly the same chance.
In one check of 60,000 rolls of 1 to 6 with this generator, each face came up between 9,870 and 10,180 times, against 10,000 expected. The page takes no seed, so a list cannot be replayed. It also does not certify a draw or keep an audit trail.
Limits
The tool sets no cap on How many numbers or on the size of the range. Above 10,000 numbers, the box shows the first 10,000 so the page stays responsive, while Copy results and Download .txt include every number. One million numbers from 1 to 100 make a text file of about 2.9 MB. Browser memory is the real limit, and Cancel stops a run that takes too long.
The page needs JavaScript, Web Workers, BigInt and Web Crypto, and a browser without them shows a message instead of numbers. If clipboard access fails, the page selects the box so you can copy by hand, or points you to Download .txt when the box shows only part of the list.
Results are plain text. There is no spinning wheel, and the page keeps no history of past lists. To draw names rather than numbers, number your list or shuffle it with a related tool below.
Questions
How does a random number generator work?
It turns a source of randomness into numbers in a range. This one reads random bytes from Web Crypto, the browser's cryptographic source, keeps just enough bits for your range, and throws away values that fall outside it. Every number from the minimum to the maximum then has the same chance.
Can a random number generator be predicted?
A simple formula-based generator can be predicted once someone knows its seed or internal state. Web Crypto is a cryptographic generator, built so that its output cannot be worked out from earlier values. This page also takes no seed, so nobody can replay a list by entering the same starting value.
Do random number generators repeat numbers?
Yes, when repeats are allowed, because each draw is independent and can land on a number that came up before. Eleven draws from 1 to 10 always contain a repeat. Select No repeats to make every number in one list different; the count then cannot exceed the number of possible values.
How can I generate a list of random numbers?
Set How many numbers to the length you need, such as 7, and select Generate numbers. The list appears one number per line, ready for Copy results or Download .txt. Add No repeats for a list without duplicates. There is no cap on the length; above 10,000 the box shows the first part.
Can you make a truly random number generator?
Hardware generators measure physical noise, such as electronic or atmospheric noise. This page uses Web Crypto instead: a cryptographic generator that browsers seed from a high-quality entropy source, usually the operating system. The page does not certify a draw or keep a public record of it, which some contests and official lotteries require.
How do I get random decimals?
Set Number type to Decimals and choose Decimal places. The generator picks from evenly spaced values at that precision, so 0 to 1 at 2 places has 101 possible values, from 0.00 to 1.00. Endpoints are never rounded: one with more places than you chose gives an error.
Related tools
- Shuffle a list of lines: put names or items in random order, or sort lines and remove duplicates.
- Number the lines of a list: give each item a number, then draw from 1 to the length of the list.
- Password generator: random passwords with the length and character types you choose.
- UUID generator: random version 4 identifiers, or versions 1 and 7, singly or in bulk.