DocomintCalculatrice de Factorielle
Calculez N! (factorielle de N) — le produit de tous les entiers de 1 à N.
What is a Calculatrice de Factorielle?
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.
How to use the Calculatrice de Factorielle
- Enter a whole number, 0 or greater
- Press Calculate
- N! appears instantly, computed on your device
Formula
n! = n × (n − 1) × (n − 2) × ... × 1, with 0! = 1
Each step multiplies by the next smaller whole number down to 1 — factorials count the number of ways to arrange n distinct items in order.
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.
Common mistakes
- Assuming 0! is 0 — it's defined as 1 by mathematical convention, not calculated from the multiplication chain.
- Entering a negative number expecting an answer — factorial is undefined for negative integers.
- Expecting a decimal input to round to a nearby factorial — this calculator only accepts whole numbers.
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.
What's the largest N this can calculate?
Up to 170! — beyond that, the result exceeds what a standard double-precision number can represent accurately, so the input is capped there.
Is factorial defined for negative numbers?
Not for negative whole numbers under the standard definition used here. The Gamma function extends factorial to non-integers and some complex numbers, but that's outside what this calculator computes.
Is my numbers uploaded anywhere?
No — Calculatrice de Factorielle runs entirely in your browser using JavaScript/WebAssembly. Your numbers is never sent to a server.