Factorial Calculator
Calculate factorials, permutations, and combinations for any number with step-by-step computation
5!
120
3 digits
Step by Step
5! = 5 × 4 × 3 × 2 × 1 = 120
n! = n × (n-1) × (n-2) × ... × 1
P(n,r) = n! / (n-r)! — ordered arrangements
C(n,r) = n! / (r! × (n-r)!) — unordered selections
How to Use This Tool
Choose a mode: Factorial (n!), Permutation P(n,r), or Combination C(n,r).
Enter the value of n (and r for permutations/combinations).
View the result with full BigInt precision for large numbers.
For small factorials, see the step-by-step expansion.
About This Tool
Factorial Calculator computes factorials, permutations, and combinations with BigInt support for arbitrarily large results. See step-by-step expansion for factorials up to 20. Permutations P(n,r) count ordered arrangements, while Combinations C(n,r) count unordered selections. The result shows the exact digit count for very large numbers.
Frequently Asked Questions
Using BigInt, the calculator can compute factorials of any size — even 1000! with over 2,500 digits. There's no JavaScript precision limit with BigInt.
Use permutations when order matters (e.g., arranging books on a shelf). Use combinations when order doesn't matter (e.g., choosing team members from a group).
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