Factorial Calculator
Calculate the factorial of a number, including very large results.
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How it works
The factorial of a number n, written n!, is the product of all whole numbers from 1 up to n. Enter a value and the tool multiplies the sequence together using big-integer arithmetic, so even large factorials are computed exactly rather than as rounded scientific notation. It also reports how many digits the result has. Factorials grow extremely fast, which is why big-integer math matters. All computation runs in your browser.
n! = n × (n−1) × … × 2 × 1
Common use cases
- Computing factorials for probability and combinatorics.
- Checking a homework answer involving n!.
- Seeing how fast factorials grow by digit count.
Frequently asked questions
What is 0 factorial?
0! is defined as 1. This convention makes formulas for combinations and permutations work consistently — there is exactly one way to arrange nothing.
Can it handle very large factorials?
Yes. It uses big-integer (BigInt) arithmetic, so results with hundreds or thousands of digits are exact, not rounded. Extremely large inputs simply take a little longer.
Does it accept decimals or negatives?
No. The standard factorial is defined only for non-negative whole numbers. The tool asks for a whole number of zero or more.