LCM & GCD Calculator

Find the greatest common divisor and least common multiple of two or three integers.

How to Use This Calculator

Enter two or three positive integers. GCD is useful for simplifying fractions; LCM is used when adding fractions or scheduling repeating events.

What is the GCD used for?

Simplifying fractions and ratios — divide the numerator and denominator by the GCD to get the lowest terms.

What is the LCM used for?

Finding common denominators and the next time two repeating events coincide — like bus schedules.

What is Euclid's algorithm?

Repeatedly subtract or take the remainder: GCD(18, 12) → GCD(12, 6) → GCD(6, 0) = 6.

Can I enter zero?

Zero works: GCD(0, x) = x, but the LCM of anything with zero is 0. Negative numbers are converted to positive.

For 18 and 24:

GCD — the largest number that divides both; used to simplify fractions.
LCM — the smallest number both divide into; used for common denominators and scheduling.