Random Number Generator
Pick one or more random numbers between any two values, with or without repeats, as whole numbers or decimals.
Results
| Item | Value |
|---|
Quick Answer
To pick a random number between 1 and 100, enter 1 and 100 and press Calculate. Each of the 100 numbers has the same 1% chance. For lottery-style picks, choose No repeats, such as 6 numbers from 1 to 49.
Embed this calculator
Adjust the size if needed, then copy the code below into your page or blog. The calculator will load in an iframe and stay updated automatically.
Table of Contents
- Random Number Generator
- Quick Answer
- Related Calculators
- How This Random Number Generator Works
- How to Use the Random Number Generator
- How the Numbers Are Picked
- Key Terms
- Worked Example
- Real-Life Examples
- True Random vs Pseudo-Random
- Chance of Each Result
- Tips for Fair Draws
- Common Mistakes to Avoid
- Frequently Asked Questions
- References & Sources
How This Random Number Generator Works
Enter the lowest and highest numbers, how many numbers you want, and whether a number may come up more than once. The generator uses your browser’s secure random source and a method that gives every number in the range exactly the same chance. You can sort the results and choose decimal places.
Quick explanation: each press gives a new, independent result.
- No repeats: like drawing numbered balls from a bag without putting them back.
- Allow repeats: like rolling a die many times.
- Decimals: choose up to 6 decimal places.
How to Use the Random Number Generator
- Enter the lowest and highest numbers.
- Enter how many numbers you want.
- Choose whether numbers may repeat.
- Choose the order and decimal places.
- Press Calculate to see your random numbers, plus their sum and average.
How the Numbers Are Picked
- Range size: highest − lowest + 1 possible whole numbers
- Chance of each number: 1 ÷ range size
- No bias: random values that would favor some numbers are thrown away and drawn again
- No repeats: numbers are shuffled with the Fisher–Yates method, or redrawn if already picked
Key Terms
- Random number: a number chosen so every possible value has the same chance.
- Range: all numbers from the lowest to the highest, including both.
- With replacement: a number can be picked again, so repeats are possible.
- Without replacement: each number can be picked only once.
- Uniform distribution: every value in the range is equally likely.
Worked Example
A teacher wants to pick 3 different students from a class list numbered 1 to 28.
- Lowest = 1, highest = 28, how many = 3, no repeats
- There are 28 possible numbers, each with a 1 in 28 chance of being first
- The result is 3 different numbers, such as 4, 17 and 22
Real-Life Examples
- Giveaways: number the entries 1 to 250 and pick 1 winner.
- Lottery-style picks: choose 6 numbers from 1 to 49 with no repeats, sorted smallest to largest.
- Dice: set 1 to 6, 5 numbers, allow repeats, to roll five dice.
- Classroom: pick which student answers, or split a class into random groups.
- Sampling: choose 20 random rows from a list of 500 for a quality check.
True Random vs Pseudo-Random
- Pseudo-random: made by a formula from a starting value. Fine for games, but can be predicted if the formula is known.
- Secure random: built from hard-to-predict system data. This tool uses your browser’s secure generator.
- True random: taken from physical events, such as noise. Used by some lotteries and research labs.
Chance of Each Result
| Range | Possible numbers | Chance of one number |
|---|---|---|
| 1 to 2 (coin) | 2 | 50% |
| 1 to 6 (die) | 6 | 16.67% |
| 1 to 10 | 10 | 10% |
| 1 to 20 | 20 | 5% |
| 1 to 100 | 100 | 1% |
| 1 to 1,000 | 1,000 | 0.1% |
Tips for Fair Draws
- Agree on the rules first: set the range and number of picks before you press Calculate.
- Number the entries: give each person or item a number, then draw numbers.
- Use the first result: pressing again until you like the answer is not fair.
- Share your screen: for giveaways, let people watch the draw.
Common Mistakes to Avoid
- Using the wrong range. Check that both end numbers are included and correct.
- Allowing repeats by mistake. For winners or lottery picks, choose No repeats.
- Redrawing until you like the result. This makes the draw unfair.
- Thinking a number is due. Each draw is independent of the last.
- Asking for more unique numbers than the range holds. 1 to 10 has only 10 different numbers.
Frequently Asked Questions
Enter 1 as the lowest and 10 as the highest, set how many to 1, and press Calculate.
It uses your browser’s cryptographically secure random source, and removes bias, so each number has the same chance.
Yes. Choose No repeats. Each number will appear at most once.
Yes. For example, choose 5 numbers from 1 to 69 with no repeats. Every set of numbers has the same chance of winning.
Yes. Enter a negative lowest number, such as −50 to 50.
Yes. Set the decimal places from 1 to 6.
Yes. The lowest and highest numbers can both be picked.
Up to 10,000. With no repeats, you cannot ask for more numbers than the range holds.
No. Numbers are made in your browser and are not sent to us.
Yes. Number each entry, set the range to match, and pick the winners with no repeats.
With repeats allowed, it is 1 divided by the size of the range, such as 1 in 100 for 1 to 100.
Yes. Choose Smallest to largest or Largest to smallest.
References & Sources
| Source | Used For | Link |
|---|---|---|
| MDN Web Docs, Crypto.getRandomValues() | The secure random source this tool uses. | https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues |
| Wikipedia, Fisher–Yates shuffle | The method used for picks without repeats. | https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle |