Factorial Calculator
Calculate n! and see the multiplication laid out, for whole numbers from 0 up to 170.
6!
720
How it multiplies out
6! = 1 × 2 × 3 × 4 × 5 × 6 = 720
How it works
The factorial of n, written n!, is the product of every whole number from 1 up to n. So 6! = 1 × 2 × 3 × 4 × 5 × 6 = 720. It shows up all over counting and probability — it's the number of ways to arrange n things in a row.
There's one quirk worth knowing: 0! equals 1. That's the empty product, and it keeps the counting formulas consistent. Factorials aren't defined for negative numbers, so those return a dash.
For small values you'll see the full chain of multiplication. Larger ones grow fast — 20! already tops two quintillion — so once the number gets huge it's shown in scientific notation. The cap is 170! because 171! overflows a standard number.
Frequently asked questions
Why does the calculator stop at 170?
171! is larger than the biggest value a standard floating-point number can hold, so it would come back as infinity. Capping at 170 keeps every answer real and exact enough to trust.
What is 0! and why isn't it 0?
0! is defined to be 1. Think of it as the number of ways to arrange nothing — there's exactly one arrangement, the empty one. It also makes formulas like combinations work without special cases.
Can I take the factorial of a decimal?
Not here. The everyday factorial is only defined for whole numbers, so a decimal returns a dash. Extending it to fractions needs the gamma function, which is a different tool.