How to use Factorial Calculator
- Enter a whole number from 0 to 2000.
- Read the exact factorial.
- Copy it or use the scientific notation for huge values.
About this tool
The factorial of n is the product of all whole numbers from 1 to n, so 5! = 5 x 4 x 3 x 2 x 1 = 120. By definition 0! equals 1. Factorials count the number of ways to arrange n distinct items and appear throughout probability and combinatorics.
Factorials grow extremely fast: 20! already has 19 digits, and 1000! has 2,568 digits. The calculator uses big-integer arithmetic to keep every digit exact.
Frequently Asked Questions
- Why is 0! equal to 1?
- There is exactly one way to arrange zero items, and defining 0! as 1 keeps formulas for combinations consistent.
- Can I calculate the factorial of a decimal?
- Not here. The gamma function extends factorials to non-integers, but this tool supports whole numbers only.
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