Helpful Toolbox

Factorial Calculator

Type a whole number and get its exact factorial — no rounding, no limits, no data ever leaves your browser.

📖 How it works & FAQ

What is a factorial?

The factorial of a non-negative whole number n, written n!, is the product of every whole number from 1 up to n. So 5! = 5 × 4 × 3 × 2 × 1 = 120. By definition 0! = 1, because there is exactly one way to arrange an empty set. Factorials show up all over math — they count permutations (how many ways you can order n items), power the binomial coefficients in probability, and appear in Taylor series across calculus.

Why exact results matter

Factorials grow astonishingly fast. 13! already exceeds what a standard JavaScript number can hold precisely, so most calculators quietly switch to scientific notation and drop the exact digits. This tool uses JavaScript BigInt arithmetic, which stores whole numbers of unlimited size. That means the answer you see is the complete, exact integer — every last digit — no matter how large n is. For giant results we also report the total digit count, which is often the most useful number to have.

How to use it

  1. Type a non-negative whole number into the box (for example 10, 52, or 200).
  2. Press Calculate n! or hit Enter.
  3. Read the summary line for a quick preview and the digit count.
  4. Copy the full exact result from the result box if you need it elsewhere.
  5. Use Clear to reset and try another value.

Everything runs locally in your browser — nothing is ever uploaded.

FAQ

What is the largest n I can enter?
There is no fixed cap, but very large values (above ~50,000) take longer and produce numbers with hundreds of thousands of digits. We show a warning so you know to expect a pause.
Why is 0! equal to 1?
An empty product equals 1, and there is exactly one arrangement of zero items. This convention keeps formulas like permutations and combinations consistent.
Can I compute the factorial of a decimal or negative number?
No. The factorial is only defined here for non-negative whole numbers. Decimals and negatives are rejected. (The gamma function extends factorials to other values, but that is beyond this tool.)
Are the results exact?
Yes. BigInt keeps every digit precisely, so there is no rounding or scientific-notation approximation.