# Factorial Calculator

> Calculate the factorial of a non-negative integer (n!).

Page: https://askcalculators.com/calculator/factorial-calculator/
Definition: https://askcalculators.com/calculator/factorial-calculator/definition.json
JSON Schema: https://askcalculators.com/calculator/factorial-calculator/schema.json
Version: 7.0.0
Maintained by: AskCalculators (software project; not a credentialed reviewer)
Qualified review: pending. Automated checks do not establish professional approval.
Page status: Live
Review status: Pending

## Use
Open the calculator page and enter values. Query-string parameters can restore and bookmark a calculation.
Example: https://askcalculators.com/calculator/factorial-calculator/?number=5

## Inputs
- number: Number; type=number; optional; default=5

## Outputs
- result: Result; format=text; primary

## Formula
n! = product of every whole number from 1 through n, with 0! = 1.

## Rules
- Empty optional inputs are undefined, not zero.
- Hidden conditional inputs are ignored.
- Do not invent missing required inputs.