The factorial of n, written n!, is the product of all the whole numbers from 1 to n. So 5! is 5 × 4 × 3 × 2 × 1 = 120. It counts the number of ways to arrange n distinct items in order.

Zero factorial is defined as 1. There is exactly one way to arrange nothing, the empty arrangement, and the value 1 also keeps the combination and permutation formulas working when r equals n.

Why show every digit instead of rounding?

Factorials grow extremely fast, and 20! already passes two quintillion. A normal calculator switches to a rounded approximation, which is no good for exact counting, so this tool keeps the full integer.

Factorial Calculator

Compute n! exactly, with every digit shown, even when the number runs to hundreds of digits. You also get the digit count and a scientific-notation summary. A free factorial calculator that runs in your browser, with no rounding and no sign-up.

Compute n! exactly, with every digit kept even when the result runs to hundreds of digits. Enter a whole number and read the full value, a digit count and a scientific-notation summary. Unlike a basic calculator that rounds large factorials, this keeps the exact integer, which matters for counting and probability.

Exact, step-by-step answers
100% free
No sign-up, no app
Instant as you type
Works offline after first load

Whole number (n)

5! (5 factorial)

120

5! = 5 × 4 × 3 × 2 × 1

That is 1.20 × 10^2, with 3 digits in total.

How to use it

1
Enter n

Type a whole number. The factorial of n is the product of every whole number from 1 up to n.
2
Read n! exactly

The full exact value is shown, with digits grouped so a long number stays readable.
3
See the summary

Alongside the exact value you get the digit count and a scientific-notation form for very large results.

When it comes in handy

Probability and counting

Factorials are the building block of combinations and permutations, so an exact value keeps those counts correct.

Maths coursework

Check a factorial by hand against the exact answer, including large cases a basic calculator rounds off.

Programming reference

Confirm an expected factorial value when testing code, with every digit intact rather than a floating-point approximation.

Instant, exact & 100% in your browser

The maths runs right here in your browser, with fractions and whole numbers kept exact rather than rounded along the way. Nothing you type is sent to a server, there is no sign-up and no limit, and once the page has loaded it keeps working even with no connection.

Frequently asked questions

What is a factorial?: The factorial of n, written n!, is the product of all the whole numbers from 1 to n. So 5! is 5 × 4 × 3 × 2 × 1 = 120. It counts the number of ways to arrange n distinct items in order.
What is 0 factorial?: Zero factorial is defined as 1. There is exactly one way to arrange nothing, the empty arrangement, and the value 1 also keeps the combination and permutation formulas working when r equals n.
Why show every digit instead of rounding?: Factorials grow extremely fast, and 20! already passes two quintillion. A normal calculator switches to a rounded approximation, which is no good for exact counting, so this tool keeps the full integer.

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How to use it

Enter n

Read n! exactly

See the summary