Calculators
Random number 1 to 100
Select Generate numbers to get one whole number from 1 to 100. Each of the 100 numbers has the same 1 in 100 chance on every draw, and both 1 and 100 can come up. Raise How many numbers for a list, and select No repeats if every number in it must differ. The draw runs in your browser.
How to pick a random number from 1 to 100
The page opens set to one whole number from 1 to 100, so one click gives an answer. The steps use the labels shown on this page.
- Check that Minimum value is 1, Maximum value is 100 and How many numbers is 1. Number type stays on Integers.
- Select Generate numbers. The number appears in the box under Your numbers.
- Select Generate again for a fresh draw. Each draw is new and does not depend on earlier results.
- To keep a result, select Copy results or Download .txt. The download is random-numbers.txt, with one number per line.
Changing any setting clears the last result, so select Generate numbers again. Reset puts back 1 to 100 with one number and empties the box. Cancel stops a long run, such as a request for a billion numbers.
The chance of each number
Every whole number from 1 to 100 has a 1 in 100 chance, or 1%, on each draw. Both ends count: 1 and 100 are as likely as 50. With repeats allowed, draws do not affect each other, so the next number matches the last one with a chance of 1 in 100, and no number is ever due.
In one check of this generator in Chrome, 1,000,000 draws gave each number between 9,674 and 10,258 times, against an expected 10,000 each. Fair draws almost never come out exactly even. At this size, a gap of a few hundred from 10,000 is normal.
Equal chance does not mean that every number shows up in turn. In 100 draws, a given number such as 7 appears at least once only 63.4% of the time, and it takes 69 draws for that chance to pass one half.
How the generator avoids bias
The generator takes random bytes from Web Crypto, the browser's cryptographic random source, and uses rejection sampling. It keeps the lowest 7 bits of a byte, a value from 0 to 127. The values 0 to 99 become the numbers 1 to 100. The values 100 to 127 are thrown away, and the generator reads the next byte.
The shortcut of dividing a byte by 100 and keeping the remainder would be unfair. A byte has 256 values, and 256 is not a multiple of 100, so 1 to 56 would come up 3 times in 256 (about 1.17%) and 57 to 100 only 2 times in 256 (about 0.78%). Throwing away the extra values leaves exactly two byte values for each number instead. Since 100 of every 128 values are kept, the generator uses 1.28 random bytes per number on average.
Several numbers and the chance of a repeat
Set How many numbers above 1 to get a list, one number per line. With repeats allowed, each draw can land on any of the 100 numbers, so a list can hold the same number twice. The chance of at least one repeat grows quickly:
| Numbers drawn | Chance of at least one repeat |
|---|---|
| 2 | 1.0% |
| 5 | 9.7% |
| 10 | 37.2% |
| 13 | 55.7% |
| 20 | 87.0% |
| 30 | 99.2% |
Each figure is 1 minus the chance that all draws differ. For 3 draws that chance is 100 × 99 × 98 divided by 100 × 100 × 100, or 97.02%. This is the birthday problem with 100 days.
From 13 draws on, a repeat is more likely than not. A list of 10 numbers with repeats allowed holds a repeat more than a third of the time, so a list of turns or prizes needs No repeats.
No repeats
Select No repeats to get different numbers in one list. The generator then draws without replacement: each number it picks leaves the pool, and the next draw chooses evenly from the numbers left. How many numbers can then be at most 100 in this range. With 101 or more, the page shows an error beside How many numbers and generates nothing.
Every remaining number has the same chance on each draw, so every order of the list is equally likely. Set How many numbers to 100 with No repeats to get every number from 1 to 100 exactly once, in random order. That list can set a full order of turns for a game or a class: read it from the top.
No repeats applies inside one list only. Generate again starts a new list, which can repeat numbers from the list before.
Other ranges and decimals
Change Minimum value or Maximum value to draw from another range. Both ends are always included, so 0 to 100 has 101 possible numbers and 1 to 1000 has 1,000. Negative numbers work too, such as -50 to 50.
Type the numbers without commas or exponents. Each number in the range has the same chance, which is 1 divided by the count of possible numbers: 1 in 101 for 0 to 100 and 1 in 1,000 for 1 to 1000.
For numbers with a decimal part, set Number type to Decimals and choose Decimal places. At 2 places, 1 to 100 means 1.00, 1.01 and so on up to 100.00: 9,901 possible values, each equally likely. At 1 place there are 991. An endpoint that needs more decimal places than you chose gives an error, because the tool never rounds it.
Limits
The generator keeps no history. It cannot stop a number from coming back in a later list or replay a past draw, and the result is cleared when you leave the page. It does not certify a draw or keep an audit trail, so it cannot prove to other people that a draw was fair.
Numbers appear as text; there is no spinning wheel. To pick a name, number your list or shuffle it with one of the related tools below.
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, and Copy results and Download .txt include every number. Very large requests are limited by the browser's memory. The page needs JavaScript and Web Crypto, and a browser without them shows a message instead of numbers.
Questions
What is the most common random number between 1 and 100?
On this generator, none. Each whole number from 1 to 100 has the same 1 in 100 chance on every draw, because rejection sampling gives each number exactly two of the accepted byte values. In one check of 1,000,000 draws with this generator, every number came up between 9,674 and 10,258 times.
Is 37 more likely than other numbers?
Not here. Questions about 37 concern how people choose, which this page does not measure. The generator does not choose like a person: 37 has the same 1 in 100 chance as 1, 50 or 100. In the same check of 1,000,000 draws, 37 came up 9,971 times, close to the expected 10,000.
Can you give me 20 random numbers?
Yes. Set How many numbers to 20 and select Generate numbers. The 20 numbers appear one per line, ready to copy or download, and No repeats makes them all different. With repeats allowed, 20 draws from 1 to 100 contain at least one repeat 87.0% of the time.
How do I pick numbers from 1 to 100 with no repeats?
Select No repeats, set How many numbers to the count you need, up to 100, and select Generate numbers. Each number then appears at most once in that list. A count of 100 gives all 100 numbers in random order. A new list from Generate again can reuse numbers from the last one.
Can you pick a number between 1 and 100?
Yes. This page opens with Minimum value 1, Maximum value 100 and How many numbers 1, so selecting Generate numbers picks one whole number right away. Select Generate again for another pick. Every pick is independent of the ones before, so the same number can come up twice in a row.
Related tools
- Shuffle a list of lines: put names or items in random order, also with Web Crypto randomness.
- Number the lines of a list: give each name a number, then draw from 1 to the length of the list.
- Generate a random password: random characters instead of numbers.