Category: Calculators
Factorial Calculator
Compute n! exactly, with the full result shown
Enter a whole number n to compute n!, the product of every whole number from 1 to n, shown in full with thousands separators.
3 628 800
7 digits
n! is the product of every whole number from 1 to n, and 0! is defined as 1. Factorials grow extremely fast: 20! already has 19 digits.
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What this tool does
The factorial of n multiplies every whole number from 1 up to n together. This calculator computes it exactly using arbitrary-precision arithmetic, so the full digit string is correct even for values with hundreds of digits, rather than the rounded approximation a regular calculator gives once the result gets large.
How to use it
- Enter a whole number from 0 to 500.
- Read the exact value of n! underneath, grouped in thousands for readability.
- Check the digit count for a sense of how large the result is.
Privacy
This tool runs entirely in your browser. Your input is never uploaded, stored or shared — closing the tab removes it.
Frequently asked questions
- Why is 0! equal to 1?
- By convention, the product of no numbers at all (an empty product) is defined as 1, which keeps formulas like combinations and permutations consistent for n = 0.
- Why does the calculator stop at 500?
- 500! already has over 1,100 digits. Larger inputs are still computable, but the result becomes impractically long to read, so 500 is a conservative, fast and still very generous limit.
- Why not just use a regular calculator?
- Most calculators and even JavaScript's built-in numbers lose precision well before 170!, and overflow to infinity right after. This tool uses exact big-integer arithmetic instead, so every digit is correct.