About this GCD & LCM
GCD (Greatest Common Divisor) and LCM (Least Common Multiple) are fundamental concepts in arithmetic, especially for working with fractions.
Who this calculator is for
- Students simplifying fractions or checking divisibility homework.
- Teachers and tutors explaining factors, multiples, and common denominators.
- Anyone comparing two whole numbers to find shared factors or shared multiples.
When to use it
- Use it before adding or subtracting fractions to find a lowest common denominator.
- Use it when reducing ratios or checking whether two integers are coprime.
- Use it as a quick divisibility helper before prime factorization or long division.
How to use this calculator
- Enter Number A.
- Enter Number B.
Key assumptions
- This calculator is intended for whole-number inputs.
- Negative signs do not change the GCD or LCM magnitude because the formulas use absolute values.
- Non-integer or blank inputs return an invalid result instead of being rounded silently.
Accuracy and testing
Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.
How this calculator works
GCD: Found using the Euclidean algorithm. LCM: Calculated as (|A × B|) / GCD(A, B).
Understanding your results
GCD is the largest number that divides both inputs evenly. LCM is the smallest number that both inputs divide into.
Example scenarios
12 and 18
GCD is 6. LCM is 36.
5 and 7
GCD is 1 (they are coprime). LCM is 35.
Key Features
- Instant Calculation
- Private & Secure
- Mobile Optimized
Glossary of Terms
- Coprime
- Two numbers whose GCD is 1.
- Factor
- A number that divides another number evenly.