Factorial Calculator
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A comprehensive factorial and combinatorics calculator. Computes n! for n from 0 to 170 exactly - values beyond 170 exceed JavaScript's floating-point precision and are flagged. The expanded product (1 × 2 × 3 × … × n) is shown for n ≤ 20. Stirling's approximation (n! ≈ √(2πn) × (n/e)^n) is shown for large n. Double factorial n!! (product of every other number down to 1 or 2) is computed side by side. The nPr and nCr combinatorics modes let you find permutations and combinations with the factorial formula shown. All results are displayed in standard and scientific notation.
How to Use
- 1Enter a non-negative integer n (0–170) in the input field
- 2Click Calculate to see n!, the expanded product, and Stirling's approximation
- 3Double factorial n!! and the scientific notation are shown automatically
- 4Switch to nPr / nCr mode to calculate permutations and combinations - enter n and r
- 5The factorial table at the bottom shows values for n = 0 to 20
Features
- n! for n = 0 to 170 with expanded product (n ≤ 20)
- Stirling's approximation for large n
- Double factorial (n!!)
- nPr and nCr combinatorics calculator
- Scientific notation and standard display
- Factorial table n = 0–20
- 100% browser-based
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