BYTETOOLS

Factorial Calculator

Calculate the factorial of any number (n!) exactly using BigInt, and see the full result plus its digit count. Free online factorial calculator.

19
20! digit count
exact
Result length

20! =

2432902008176640000

  • Exact factorials with BigInt — no rounding
  • Shows the complete result, every digit
  • Reports the number of digits in the answer
  • Handles very large n while staying responsive
  • Friendly guard against absurd inputs
  • Private, client-side computation

How to use the Factorial Calculator

  1. 1

    Enter a non-negative whole number, n.

  2. 2

    Read the exact value of n! in the result box.

  3. 3

    Check the digit count to gauge the size of the answer.

  4. 4

    Copy the full result to your clipboard.

About the Factorial Calculator

The ByteTools Factorial Calculator computes n! — the product of every whole number from 1 up to n — with exact precision. Instead of switching to scientific notation like a pocket calculator, it uses JavaScript BigInt to show every single digit, along with a count of how many digits the answer has.

Factorials appear throughout probability, combinatorics, statistics and calculus, and they grow astonishingly fast: 20! already exceeds two quintillion. This tool is perfect for students verifying homework and for anyone who needs the true value rather than a rounded approximation.

All computation runs locally in your browser. Nothing is uploaded or stored, and a sensible cap keeps very large inputs from freezing your device, with a friendly note if you exceed it.

Frequently asked questions

What is a factorial?

A factorial, written n!, is the product of all positive integers from 1 to n. For example, 5! = 5 × 4 × 3 × 2 × 1 = 120. Factorials count the number of ways to arrange n distinct items in order.

What is 0 factorial?

By definition, 0! equals 1. It represents the single way to arrange an empty set — doing nothing. This convention keeps formulas for permutations and combinations consistent, which is why the calculator returns 1 for an input of zero.

Why use BigInt for factorials?

Factorials outgrow the range of ordinary floating-point numbers very quickly, so a normal calculator rounds them. BigInt stores integers of any size exactly, so this tool shows the precise, full-length value with no approximation.

How many digits does a large factorial have?

The digit count grows rapidly: 100! has 158 digits and 1000! has 2568. The calculator reports the exact digit count alongside the number, which is useful when the value is too long to read at a glance.

Is there a limit on n?

Yes, the input is capped so an extreme value cannot freeze your browser. If you exceed the limit, the tool shows a note asking for a smaller number rather than attempting an impractical calculation.

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