Factorial Calculator
Enter a whole number below to instantly get its factorial.
5!
120
What Is a Factorial?
n! multiplies every whole number from n down to 1. It grows extremely fast — factorials are the reason the combination and permutation calculator works the way it does.
Worked example
Calculate 6!.
6 × 5 × 4 × 3 × 2 × 1 = 720
6! = 720
Frequently Asked Questions
What is a factorial?
A factorial, written n!, is the product of every whole number from n down to 1. 5! = 5 × 4 × 3 × 2 × 1 = 120.
What is 0! equal to?
0! is defined as 1, not 0. This isn't arbitrary — it makes formulas like the combination formula work correctly for edge cases, such as choosing 0 items from a set.
What is a factorial used for?
Factorials count the number of ways to arrange a set of items in order, and they're the building block behind the combination and permutation formulas.
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