Factorial Calculator
Compute n! (the product of all positive integers up to n) exactly using arbitrary-precision arithmetic, plus the double factorial n!!.
Inputs explained
- n (non-negative integer) — A whole number from 0 to 500. Results are exact, never rounded to infinity.
How to use it
- Fill in the fields above — each input has a hint describing exactly what to enter
- Press Calculate to get your result instantly, right on this page
- Copy the result, save the tool to favorites, or share and embed it anywhere
Understanding the result
Example: 10! = 3,628,800 and 10!! = 10 × 8 × 6 × 4 × 2 = 3,840.
Frequently asked questions
What is 0! and why isn't it 0? By definition 0! = 1, because factorial counts the number of ways to arrange zero items, and there's exactly one way to arrange nothing.
What's the difference between n! and the double factorial n!!? n! multiplies every integer from 1 to n, while n!! multiplies only every other integer (n, n−2, n−4, ...), so they diverge quickly — for example 5! = 120 but 5!! = 5×3×1 = 15.
Is the Factorial Calculator free to use? Yes — it is completely free, with no sign-up, no download and no usage limits. You can use it as often as you need.
Is my data private? Yes. The calculation runs entirely in your browser — the values you enter are never sent to our servers, stored or shared with anyone.
What information do I need? Just the following: n (non-negative integer). Each field includes a hint explaining exactly what to enter.
Can I use it on my phone? Yes — the tool is fully responsive and works on any device, and the same calculator is available in the EasyWorkCalcs mobile app.
Privacy
Everything you enter into the Factorial Calculator is processed entirely in your browser. Nothing is uploaded, stored or shared — your data stays on your device.