DocomintFactorial Calculator
Calculate N! (N factorial) — the product of every whole number from 1 up to N.
Factorials count the number of ways to arrange N distinct items in order, which is why they show up constantly in probability and combinatorics homework (how many ways can 5 books be shelved? 5! = 120) — this computes it directly rather than making you multiply out a long chain by hand.
Example: 8! (8 factorial) is 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1 = 40,320 — the number of distinct orders 8 different books could be arranged on a shelf.
How it works
- Enter a whole number, 0 or greater
- Press Calculate
- N! appears instantly, computed on your device
Frequently asked questions
What is 0! (zero factorial)?
0! is defined as 1, not 0. This isn't arbitrary — it's the standard mathematical convention that keeps combinatorics formulas (like counting the number of ways to arrange zero items, which is exactly 1 way: doing nothing) consistent.
Why does factorial grow so fast?
Each step multiplies by an increasingly large number rather than adding one, so it compounds. 10! is already 3,628,800, and by 20! the result is over 2.4 quintillion — factorials outgrow exponential functions for large enough N.
Is my numbers uploaded anywhere?
No — Factorial Calculator runs entirely in your browser using JavaScript/WebAssembly. Your numbers is never sent to a server.