Random Number Generator

Set a range and a count, and every number gets the same chance

This random number generator picks the number of whole numbers you ask for at random between a minimum and a maximum. Every number in the range has the same probability, and the result is fixed the moment you press Draw. If the thing you are choosing from already carries numbers, such as seat 1 to 30 in a classroom, 1 to 49 for a set of six, or raffle tickets 000 to 999, you can draw straight away without typing out a list of names.

By default, the same number cannot appear twice in one draw. Numbers you want to skip from the start, like an absent student's seat, go in the exclude box or can be clicked on the number board. When you draw in several rounds, switch on continue mode and numbers drawn earlier stay out of later rounds. The board under the result colors the numbers drawn now, the ones removed earlier and the ones you excluded.

Why draw numbers instead of picking by hand

When you choose one person from a group or pick a raffle winner, a host who chooses by hand is often doubted even if the result was fair. If you announce the rules first (range, count, repeats) and draw on a screen everyone can see, everyone can confirm that nobody knew the outcome in advance. These are the situations where the tool fits best.

• Deciding turns in class or in a meeting: draw from 1 to 30 one at a time with continue mode on, and nobody is called twice. The board shows at a glance which numbers have not been called.
• Raffle ticket draws: with the range 000 to 999 and zero padding on, results look like the tickets (007), and Full screen puts them on the event display.
• Picking problems, pages or an order: choose 10 exercises to review out of 1 to 120, or a presentation order from 1 to 8, whenever the number itself is what you need.
• Games and learning probability: draw from 1 to 6 several times with repeats allowed to use it as a die, or enter your own numbers and compare how many you match with the probability bars.

How to draw

1. Press a common-range button (1–10, 6 of 49, 1–100, Dice 1–6, 000–999) or type your own minimum and maximum. Negative numbers and zero work, from -1,000,000,000 to 1,000,000,000.
2. Set how many to draw, from 1 to 1,000. The − and + buttons next to the box change it by one.
3. Check the method. Keep the first switch on if the same number must not come up twice, and turn on continue mode if you draw in several rounds.
4. Press Draw, or press Enter in an input box. On a narrow screen the page scrolls to the result.
5. With several results, each card shows where it came in the draw. Low to high and High to low only sort the same result; they do not draw again.
6. Copy result gives you the separator you need (comma, space or new line). Copy settings link builds an address that holds the range, count, method and exclusions, so the same setup opens again.

No repeats, repeats allowed and continue mode

The three methods differ in two ways: whether the same number can appear within one draw, and whether earlier numbers become candidates again in the next draw. In statistics, taking balls out without putting them back is sampling without replacement, and putting them back is sampling with replacement.

With no repeats, you cannot draw more numbers than are left. Asking for 11 numbers from 1 to 10 shows an error. Continue mode goes together with no repeats, so choosing repeats allowed turns it off. When continue mode has drawn the whole range, the summary line says so, and Restore in the statistics box brings back the original range. You can also click a single removed number on the board to put only that one back.

How the chances are calculated

"Chance for one number" in the statistics box is the probability that one particular number is in this result. With n numbers left and k to draw, it is k ÷ n without repeats. With repeats it is the chance of showing up at least once in k draws, 1 − (1 − 1/n)^k. The display is rounded to two decimals, and anything below 0.01% reads "less than 0.01%".

In continue mode, the chance for each remaining person rises as the pool shrinks, but at every step the remaining candidates are equally likely. Looking at the whole run, each of the 30 people is called exactly once in 30 calls, so nobody is at a disadvantage.

Choosing 6 of 49 and the number of combinations

The 6 of 49 button fills in the range 1 to 49 with six numbers. Choosing 6 numbers from 1–49 gives C(49,6) = 13,983,816 possible combinations, and every combination is equally likely. Using a generator does not change the odds of any game: a set you generate has exactly the same chance as one you pick by hand.

If you enter your own six numbers in the box, the page draws a bar chart of how many of them you can expect to match. The bars use the hypergeometric formula C(6, x) × C(43, 6 − x) ÷ C(49, 6), and the values are in the table below. Three or more matches add up to about 1.86%.

This tool does not analyze past results or pick "lucky" numbers. For a real lottery, check the official odds published by its operator.

Using the number board and the exclude box

When the range has 200 numbers or fewer, the board shows one cell per number. Click a cell and the number goes into the exclude box and the cell is struck through; click again to bring it back. It works well when you look down an attendance list and click the absent seats. With a keyboard, enter the board, move with the arrow keys and press Enter or Space.

• In the exclude box, separate numbers with commas or spaces, and join a run with a tilde (~) or a hyphen (-), as in "4, 13, 20~25". Negative runs look like -10~-5.
• Numbers outside the range do no harm and do not change the pool. Removing 4, 13 and 20~25 from 1–100 leaves 92 candidates.
• If anything is not a number, the page tells you which item it could not read and stops the draw.
• When the range is larger than 200, or the numbers are too long to fit in a cell (around 1,000,000, say), the board switches to up to 100 cells, each a block of numbers. For 000–999 a cell holds 10 numbers, and the more a cell is filled, the more numbers in that block are out. A cell that holds a number drawn now is highlighted.

How the result is decided

Numbers come from 32-bit random values returned by the browser's Web Crypto crypto.getRandomValues(), which MDN describes as providing cryptographically strong random values. Taking such a value modulo the size of the range, however, creates a bias. For a range of 2,000,000,001 numbers (-1,000,000,000 to 1,000,000,000), 2³² = 4,294,967,296 leaves a remainder of 294,967,294 when divided by that size, so plain modulo would make the first 294,967,294 values 1.5 times as likely as the rest. This tool throws away any value that lands in that leftover part and asks for a new one (rejection sampling), so all candidates stay equally likely.

To draw several numbers without repeats, it picks k different positions among the candidates so that every combination is equally likely, then shuffles their order evenly so the "drawn order" is random too. Excluded runs and numbers removed earlier are handled as lists of ranges, so even a range of two billion numbers never builds a full list.

• The spinning in Normal and Slow is only for show. The final numbers are fixed before the motion starts, and Reveal all or Show the rest now give the same result.
• Numbers not yet revealed do not show up early on the board, the scale or the check of your numbers.
• If your device has reduced motion turned on, the numbers appear one after another without spinning.

Common misconceptions

• The same number twice in a row means it is broken: with repeats allowed, that is normal. Drawing twice from 1–6 gives the same number with probability 1/6 (16.67%). Drawing 10 times from 1–100, the chance that some number comes up again is 37.18%, and drawing 23 times from 1–365 it is 50.73%.
• A number that has not appeared for a while is due: every draw is fresh, with or without repeats, so earlier results do not affect the next one. Only in continue mode are earlier numbers removed from the pool.
• Drawing again until you like it is still fair: once you redraw after seeing the result, it is as if the host were choosing the result. Announce in advance that the first result counts.
• Random numbers should look evenly spread: random results often look clustered. Drawing 6 from 1–45 frequently includes two neighbours, such as 17 and 18.

Running a fair draw

1. Check that both ends of the range match the first and last number on the tickets.
2. Put numbers that must be skipped, such as absentees or people who already won, into the exclude box or onto the board beforehand.
3. Decide whether one person may be picked twice, and set the repeat method to match. If you draw in rounds, turn on continue mode.
4. Tell the participants the range, count and method, and draw while everyone watches the screen. For a raffle that needs some suspense, combine the Slow or One by one effect with Full screen.
5. When every number is revealed, the draw log keeps the round, time, range and result. Use Copy log to paste it into an announcement.

Limits of this tool

• It draws whole numbers only, not decimals or random strings.
• You can draw 1 to 1,000 numbers at a time. If you need more, turn on continue mode and draw in parts, and the parts never overlap.
• The board lets you click single numbers only when the range has 200 numbers or fewer and each number fits in its cell. Otherwise, write runs in the exclude box.
• Results and the draw log stay on this screen, are not stored on a server and vanish on reload. A copied log can be edited, so it is not enough to prove how a draw went in a dispute.
• The numbers appear on screen and stay in the log and the clipboard, so do not use them for secrets such as passwords or verification codes.
• Randomness depends on what the browser provides. In a very old browser without Web Crypto, the tool falls back to ordinary random numbers (Math.random).

Reference date 2026-10-22.

Sources

• 01MDN: Crypto.getRandomValues()Fills an array with cryptographically strong random values, up to 65,536 bytes at a time
• 02W3C: Web Cryptography APIThe browser standard that defines getRandomValues
• 03Lemire, D. (2019). Fast Random Integer Generation in an Interval. ACM TOMACS 29(1)How to turn random bits into integers in a fixed interval without statistical bias

Frequently asked questions

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