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Factorial Calculator

Factorial Calculator — get the answer instantly in your browser, free and private.

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About the Factorial Calculator

A factorial calculator is a free online tool that instantly computes the factorial (n!) of any non-negative integer—the product of that number multiplied by every positive whole number below it. This browser-based calculator handles large numbers that would be tedious to calculate by hand, from small values like 5! = 120 all the way up to 170! and beyond, displaying results in standard or scientific notation for easy reading. It requires no sign-up, no account, and no data is uploaded anywhere—everything runs entirely in your browser for complete privacy and instant results.

How Factorial works

How the Factorial Calculator Works

A factorial (written as n!) means multiplying a number by every positive whole number below it, down to 1. The formula is:

n! = n × (n - 1) × (n - 2) × (n - 3) × ... × 1

Worked Example:

Calculate 6!

  1. Start with 6
  2. Multiply: 6 × 5 × 4 × 3 × 2 × 1
  3. Compute step-by-step: 6 × 5 = 30, then 30 × 4 = 120, then 120 × 3 = 360, then 360 × 2 = 720, then 720 × 1 = 720
  4. Result: 6! = 720

Using the Calculator: Simply enter your number (0 to 170) into the input field and click calculate. The tool instantly computes the result and displays it. For very large factorials, the result appears in scientific notation (for example, 20! = 2.432902008e+18) to keep the display readable. Note: By mathematical convention, 0! = 1.

How to use

  1. Enter your values as shown in the input box.
  2. The result is calculated instantly.
  3. Click Copy to use it.

Common uses

  • Probability and statistics: Calculate combinations and permutations for analyzing survey results, lottery odds, or event outcomes where arrangement matters
  • Combinatorics problems: Determine how many ways objects can be arranged or selected, essential for discrete mathematics and counting problems
  • Password and security analysis: Compute total possible character arrangements to understand password strength and entropy in security calculations
  • Physics and chemistry: Calculate molecular arrangement possibilities or quantum state permutations in physics equations and chemical equilibrium problems
  • Computer science algorithms: Solve problems involving sorting, scheduling, and graph theory that depend on computing factorials for complexity analysis

Frequently asked questions

What does the exclamation point mean in math?
The exclamation point (!) is a symbol that means factorial. It tells you to multiply the number by every positive whole number below it. For example, 5! means 5 × 4 × 3 × 2 × 1 = 120.
Why does 0! equal 1?
By mathematical convention, 0! = 1. This definition makes formulas in combinatorics and probability work correctly, and it aligns with the Gamma function used in advanced mathematics.
Can this calculator handle very large numbers?
Yes, the calculator handles numbers up to 170. Beyond that, factorials grow so astronomically large that they exceed standard computer number precision, but you can see how fast factorials grow by trying 50!, 100!, or 150!
What is a factorial used for in real life?
Factorials are used in probability (like calculating odds), statistics (permutations and combinations), computer science (algorithm complexity), password strength analysis, and physics equations involving particle arrangements or quantum states.
Is my data safe when using this calculator?
Completely safe. This is a browser-based tool that runs 100% on your device—nothing is uploaded to any server, so your calculations remain entirely private and your data is never stored or shared.