Factorial Calculator

Calculate factorials instantly. Free online factorial calculator for permutations, combinations, and probability.

The Factorial Calculator computes n! (n factorial) for any non-negative integer. Factorials are fundamental in probability, permutations, combinations, and many areas of mathematics and science. Whether calculating possible arrangements, solving probability problems, or working with series expansions, this tool provides instant factorial values with support for large numbers.

Common use cases

  • Probability calculations
  • Permutation counting
  • Combination calculations
  • Taylor series computations
  • Cryptographic key calculations

How to use

  1. Enter a non-negative integer
  2. Click calculate for the factorial
  3. View the complete result
  4. See the multiplication sequence
  5. Copy large results for use

FAQ

What is factorial?

n! = n × (n-1) × (n-2) × ... × 2 × 1. For example, 5! = 5×4×3×2×1 = 120.

What is 0! (zero factorial)?

0! = 1 by definition. This is necessary for mathematical consistency in combinations and other formulas.

Why do factorials grow so fast?

Each step multiplies by an increasing number. 10! is already 3,628,800; 20! has 19 digits.

Are there factorials for fractions?

Yes, the gamma function extends factorials to all numbers: Γ(n+1) = n! for positive integers.