Factorial Calculator — Compute n! Step by Step (Free)

Use this free factorial calculator to compute n! for any whole number. Enter n and you’ll get the exact value (even for large numbers), the full expansion n × (n−1) × … × 1, and the number of digits.

How to use the calculator

1. Enter a non-negative whole number n.
2. Press Calculate.
3. Read n!, the expansion, and the digit count.

What is a factorial?

A factorial is the product of a whole number and every whole number below it down to 1: n! = n × (n−1) × … × 2 × 1. By definition 0! = 1. Factorials count the ways to arrange n items and appear throughout permutations and combinations.

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Frequently asked questions

What does n! mean?

It means the product of all whole numbers from n down to 1. For example, 5! = 5 × 4 × 3 × 2 × 1 = 120.

Why is 0! equal to 1?

There is exactly one way to arrange zero objects (the empty arrangement), so 0! is defined to be 1.

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Can it handle large numbers exactly?

Yes — it uses exact big-integer arithmetic, so values like 20! = 2,432,902,008,176,640,000 are exact.

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Read the full lesson: learn the method step by step.

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