Factorial Calculator
A factorial, written with an exclamation mark, multiplies a whole number by every whole number below it. Six factorial is six times five times four times three times two times one.
- Free
- Works offline after your first visit
- Saves on this device
- No sign-up
- Updated
How it works
Start at the number and multiply it by each smaller whole number, down to one. Zero factorial is defined as one, so the answer for zero is one.
Factorials grow very fast, so even moderate inputs give very large answers. This page accepts whole numbers up to 170.
Worked example
The factorial of 6 is 720.
Questions
Why is zero factorial one?
It keeps counting formulas consistent. Zero items can be arranged in exactly one way, which is doing nothing.
What are factorials used for?
They count the ways to arrange a set of items in order, such as how many ways six people can line up for a photo.
Can I use a decimal?
Factorials are for whole numbers. Other values need a different function, which this page does not cover.
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