CALCULATE WITH CONFIDENCE

Counting, Permutations & Combinations

Factorial Calculator

Calculate n factorial exactly for a non-negative integer.

Counting & Combinatorics

Enter a non-negative integer

Exact n!

Exact count

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Enter valid values to see the result.

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Quick guide

How to use this calculator

  1. Enter a non-negative integer n.
  2. Read the exact product n!.
  3. Use the definition note to distinguish 0! from an empty result.

Calculation method

Multiply the integers from 1 through n

For n greater than zero, n! is the product 1×2×⋯×n. The empty product convention defines 0! as 1.

Worked example

Factorial of 5

Multiply every positive integer no greater than five.

5! = 5×4×3×2×1 = 120

Supported inputs

Precision and limits

Discrete domain

Inputs are whole counts. Negative, fractional, grouped, and scientific-notation inputs are rejected.

Exact integers

Results use arbitrary-precision integers and are never rounded. Inputs and output size are bounded to keep the page responsive.