Factorial calculator
Calculate exact factorials from 0 to 1,000, including integers much larger than ordinary floating-point numbers can represent.
Result for the values shown.
Calculations run in your browser.
What to enter
| Input | Meaning and units |
|---|---|
| Non-negative integer | Use a whole number in the stated format. Fractions and rounding are not interchangeable with exact integer inputs. |
Understanding your result
Read Exact factorial in the units and model stated on this page. The formula n! = 1 × 2 × … × n defines the relationship; measurement accuracy and model applicability are separate from numerical precision.
Common mistakes
- Using a different mathematical definition or operation than the one stated by this tool.
Check your calculation
- Use the worked example as a known reference case, then change one input at a time and check the direction and units of the response.
Calculation checks, sources and review limits
What is the factorial of a whole number?
Enter a non-negative whole number to multiply all positive integers up to it. The same result counts arrangements of all n distinct items, when each item is used once.
Common uses
- Calculate n factorial without losing large integer digits.
- Count ways to arrange all distinct items.
How it works
Multiply every positive integer from 1 to n. By definition, 0! = 1. Only non-negative integers are supported. The 1,000 limit keeps large exact calculations quick in the browser.
Worked example
5! = 5 × 4 × 3 × 2 × 1 = 120.