Factorial Calculator
Compute n! exactly, even for large n, using arbitrary-precision big integers.
Exact factorials, no rounding
The factorial n! multiplies every whole number from 1 to n, and it grows faster than almost anything else in basic math. Ordinary calculators switch to scientific notation and lose precision quickly; this one keeps every digit using big integers.
For example 20! is exactly 2,432,902,008,176,640,000 — a value a normal number type can no longer represent precisely. Factorials power permutations, combinations, and probability, where an exact count matters.
Precise and private
The calculation uses JavaScript’s BigInt, so the answer is exact no matter how many digits it runs to. It all happens in your browser with nothing uploaded.
Frequently Asked Questions
Why use big integers?
Factorials grow explosively — 21! already exceeds what a normal JavaScript number can hold exactly. BigInt keeps every digit, so the result is exact rather than rounded.
How large can n be?
Very large, though thousands-of-digit results take a moment to compute and display. Negative numbers have no factorial.
What is 0!?
By definition 0! = 1, which the tool returns.
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