Factorial Calculator

Tool Guide

About This Tool

Factorial Calculator computes n! exactly for any non-negative integer and extends to permutations P(n,r) and combinations C(n,r) — a practical tool for combinatorics and probability.

Core Features

1. Exact large-number results: Computes factorials up to 170! with full precision.

2. Permutations P(n,r): Count ordered arrangements of r items from n.

3. Combinations C(n,r): Count unordered selections of r items from n.

How to Use

Step 1: Enter a non-negative integer n (0–170 supported).

Step 2: View the exact value of n!.

Step 3: Enter r to compute P(n,r) or C(n,r) as needed.

Use Cases

Probability: Calculate lottery odds or combination probabilities.

Math competitions: Quickly verify combinatorial calculation results.

Cryptography: Combinatorics appears in cryptographic protocol analysis.

FAQ

Q: Why is the limit 170?

A: 171! exceeds Java Script's maximum floating-point value (~1.8×10^308) and returns Infinity.

Q: What is 0!?

A: By mathematical convention, 0! = 1 (empty product), which is essential in combinatorial formulas and series expansions.