Math

GCD and LCM Calculator

Enter two whole numbers to find their greatest common divisor and least common multiple.

By TheCalcTools Updated October 17, 2026 Formula checked and tested

Your numbers

First number

Second number

Greatest common divisor

—

Least common multiple

—

Enter two positive whole numbers.

The GCD is found with Euclid’s algorithm, which repeatedly replaces the larger number with the remainder.

The LCM is the product divided by the GCD.

gcd(a, b) = gcd(b, a mod b)lcm(a, b) = a × b ÷ gcd(a, b)

Using the default values shown in the calculator:

First number	48
Second number	18

Result:

Greatest common divisor	6
Least common multiple	144

What are the GCD and LCM used for?

The GCD simplifies fractions. The LCM gives a common denominator when adding fractions and helps with repeating schedules.

What if the GCD is 1?

The numbers are called coprime. Their LCM is simply their product.