About this Factorial Calculator
Factorial Calculator computes exact factorial values for non-negative integers and is useful in combinatorics, probability and sequence work.
Formula or method
n! = n × (n−1) × … × 2 × 1, with 0! defined as 1.
Example
5! = 5 × 4 × 3 × 2 × 1 = 120.
Common uses
- Check factorial values for permutations.
- Verify combinatorics homework.
- Explore how quickly factorial growth increases.
How to use this tool
- Enter the values or text requested by the calculator.
- Choose units or options when the tool provides them.
- Select the calculation button and review the result.
- Use the formula, example and notes on this page to check whether the result fits your situation.
Important note
Factorials grow extremely quickly. This tool uses integer arithmetic and limits input to keep the browser responsive.
Frequently asked questions
What is 0 factorial?
By definition, 0! equals 1.
Can I enter decimals?
No. Factorials in this tool are defined for non-negative whole numbers.