How to use this factorial calculator
- Enter a non-negative whole number n from 0 up to 10000 in the n field.
- Press Calculate. The Result field shows n! as the exact full number — every digit, no rounding and no scientific notation, even for values with thousands of digits.
- The Calculation box shows the product expansion 1×2×3×…×n with the result underneath (the expansion is shown up to n = 200; larger inputs still return the exact result).
- Press Reset to clear the field, the result and the calculation.
The factorial of a non-negative integer n, written n!, is the product of all whole numbers from 1 up to n: n! = 1 × 2 × 3 × 4 × … × n. For example 3! = 1 × 2 × 3 = 6, 4! = 1 × 2 × 3 × 4 = 24 and 5! = 1 × 2 × 3 × 4 × 5 = 120. By convention the empty product gives 0! = 1, and 1! = 1 as well.
Factorials grow extremely fast — 20! already has 19 digits and 100! has 158 — so this tool keeps every digit exact with arbitrary-precision integer arithmetic instead of ordinary calculator rounding. Negative numbers and decimals have no factorial, so the calculator rejects them with a clear message. The whole calculation runs in your browser; nothing is uploaded anywhere.
More math tools are in Math & Statistics.