About this tool
Compute the exact factorial of a number (n!) using BigInt, so even large results are precise to the last digit. It also reports how many digits the answer has — all computed in your browser.
Frequently asked questions
What is the largest input?
Inputs are capped at a few thousand so the browser stays responsive; larger values are rejected with a notice.
What is 0!?
By convention 0! equals 1, the empty product, and the calculator returns 1 for an input of 0.