Best Free Online Developer Tools to Use in 2026
A practical, opinionated list of the best free online developer tools worth using in 2026, organized by category so you can find what you need fast.
Aug 08, 2026
Factorial Calculator
Calculate the factorial of any integer with step-by-step multiplication.
- Home
- Utilities
- Factorial Calculator
Factorial (n!)
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Permutations (nPr) & Combinations (nCr)
nPr (Permutations)
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nCr (Combinations)
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How to Use
- Calculate factorial — Enter a non-negative integer (max 5000) and click Calculate.
- View steps — See the step-by-step multiplication for smaller numbers.
- Permutations & Combinations — Enter n and r values to calculate nPr and nCr instantly.
Frequently Asked Questions
What is a factorial?
The factorial of a non-negative integer n, denoted n!, is the product of all positive integers less than or equal to n. For example, 5! = 5 × 4 × 3 × 2 × 1 = 120.
What is 0! ?
By convention, 0! = 1. This is defined as an empty product and is used in many mathematical formulas including combinations.
What is the difference between nPr and nCr?
nPr (permutations) counts ordered arrangements where order matters. nCr (combinations) counts unordered selections where order does not matter. nPr = n!/(n-r)!, nCr = n!/(r!(n-r)!).
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