Factorial Calculator (n!)
Calculate the factorial of a number.
Result
120
5! = 120
Result in all units
Step-by-step solution
n! = n × (n−1) × … × 1
What Is a Factorial?
A factorial is the product of a positive integer with all the numbers from itself down to 1. It is the foundation of permutation and combination calculations.
How is it calculated?
How Is It Calculated?
n! = n × (n−1) × (n−2) × … × 1
- Enter the number.
For example, 5! = 5×4×3×2×1 = 120. By definition, 0! = 1.
Frequently Asked Questions
Why is 0! equal to 1?
Because there is only one way to arrange an empty set and for the consistency of the formulas, 0! = 1 is accepted.