Factorial Calculator (n!)

The factorial of n, written n!, is the product of every positive integer from 1 up to n. For example 5! = 5 x 4 x 3 x 2 x 1 = 120, and each step just multiplies in the next number.

0! is defined as the empty product, which is 1 by convention. That choice keeps counting formulas for permutations and combinations working without special cases, so the tool returns 1 for an input of 0.

Yes. The engine uses arbitrary-precision integer arithmetic rather than floating point, so results stay exact to the final digit even when they run to hundreds of digits, such as the 158 digit value of 100!.

The input is capped at 100000, and entering more shows a prompt to pick a number of 100000 or less. Values near that ceiling produce enormous answers and take a moment to compute and render.

Factorials grow explosively, so the header states how many digits the result has to give you a quick sense of scale. For instance 10! is 3628800 with 7 digits, while 20! jumps to 19 digits.

The ordinary factorial is only defined for non-negative integers, so a negative input returns an error and a decimal is rejected. Extending factorials to those values needs the gamma function, which this tool does not compute.

They count arrangements: n! is the number of ways to order n distinct items. They also appear throughout probability, in combinations and permutations, and in series expansions like the one for the number e.

The result sits in a scrollable box so it never overflows the page, and the Copy button grabs the whole value at once. From there you can paste it into a document or a math tool for further work.

Yes. Every multiplication happens locally in your browser and the number you enter is never uploaded to a server.