Online Tool Store
GCF and LCM Calculator
Calculate the greatest common factor and least common multiple of two or more numbers, with prime factorizations shown. Runs entirely in your browser.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Greatest Common Factor (GCF)
Least Common Multiple (LCM)
Prime factorizations
How the GCF and LCM calculator works
- Enter two or more positive whole numbers, separated by commas or spaces.
- See the greatest common factor and least common multiple calculated instantly.
- Review each number's prime factorization for extra context.
FAQ
How is GCF calculated?
Using the Euclidean algorithm, applied pairwise across all your numbers - it repeatedly replaces the larger number with the remainder of dividing it by the smaller, until the remainder is zero.
How is LCM calculated?
Using the relationship LCM(a, b) = (a × b) / GCF(a, b), applied pairwise across all your numbers.
How many numbers can I enter at once?
As many as you like, separated by commas or spaces - the tool computes the GCF and LCM across the entire set at once.
What are the prime factorizations for?
They show the building blocks of each number, which is often how GCF and LCM are taught in school - useful for checking your own manual work.
How we compare
| Feature | Online Tool Store | Manual factor trees | Scientific calculator |
|---|---|---|---|
| Handles more than 2 numbers at once | ✓ | ✗ | ✗ |
| Shows prime factorization | ✓ | ✓ | ✗ |
| Instant, no manual steps | ✓ | ✗ | ✓ |
A quick homework-checking tool for students working through GCF and LCM problems.