The factorial n! is the product of every whole number from n down to 1, so 5! = 5 × 4 × 3 × 2 × 1 = 120. By definition 0! = 1, and factorials are only defined for non-negative integers.

How accurate is the result for large n?

Results are exact, not approximate. The calculator uses JavaScript BigInt arbitrary-precision arithmetic, so even huge factorials are computed digit-for-digit. A cap keeps the browser responsive on extreme inputs.

Is my input sent anywhere?

No. The calculator is privacy-first — n stays in your browser and nothing is transmitted to any server.

Factorial Calculator (n!)

Compute exact factorials of any non-negative integer with BigInt.

Factorial calculator

Compute n! — the product of every whole number from n down to 1 — for any non-negative integer. Results are exact, computed with arbitrary-precision BigInt arithmetic, and the digit count is shown so you can gauge the size. Remember that 0! = 1.

It is privacy-first: everything runs locally in your browser, so the number you enter never leaves your device.