Factorial Calculator
Enter n and get n! — the product of every whole number from 1 to n — computed exactly, with all digits shown. Factorials explode fast (10! already has 7 digits, 100! has 158), and most calculators quietly switch to scientific notation and lose the digits. This one keeps every single one.
Factorials count arrangements: 5! is the number of ways to order five things (120), which makes it the backbone of probability, combinatorics, and the permutation formulas behind shuffles, rankings and lottery odds.
How to use
- Type a whole number n between 0 and 1,000.
- Read n! with every digit displayed — 0! is defined as 1.
- Check the digit count to appreciate how fast factorials grow.
Frequently asked questions
What is 5 factorial?
5! = 5 × 4 × 3 × 2 × 1 = 120. It counts the ways to arrange 5 items in order — five books on a shelf have 120 possible orders.
Why is 0 factorial equal to 1?
By definition: there is exactly one way to arrange zero items (do nothing). The convention also makes formulas like n! = n × (n−1)! work for n = 1.
How big is 100 factorial?
158 digits long — roughly 9.33 × 10^157. It exceeds the number of atoms in the observable universe by a wide margin, which is why exact-digit display matters.
Where are factorials used?
Counting permutations and combinations, probability (card shuffles, lottery odds), Taylor series in calculus, and algorithm analysis. Anywhere 'how many orderings' appears, factorials are hiding.