Factorial Calculator
Compute n! exactly, even for large numbers, with big-integer math.
The factorial n! is the product of all whole numbers from 1 to n (and 0! = 1). The exact value is computed with big-integer math, so even large factorials are precise. Runs in your browser.
Compute the factorial of a number — the product of all whole numbers from 1 up to n (and 0! = 1). The result is calculated with big-integer math, so even large factorials are exact rather than rounded, and a scientific approximation plus digit count are shown for big results. Useful for combinatorics and probability. Runs in your browser.
How to use the Factorial Calculator
- Enter a non-negative whole number n.
- Read the exact value of n! (and an approximation for large n).
- Copy the full result.
Frequently asked questions
What is a factorial?
n! (n factorial) is the product of every whole number from 1 to n. For example 5! = 5 × 4 × 3 × 2 × 1 = 120. By definition, 0! = 1.
Why use big-integer math?
Factorials grow extremely fast — 21! already exceeds the largest integer JavaScript can store exactly. Big-integer math keeps every digit precise.