GCD and LCM Calculator
This GCD calculator finds the greatest common divisor and least common multiple (LCM) of two whole numbers in one step.
Last updated: September 5, 2026
Frequently asked questions
What's the GCD of 24 and 36?
12 - the largest number that divides evenly into both 24 and 36.
How is LCM related to GCD?
LCM = (a × b) ÷ GCD(a, b). For 24 and 36: (24 × 36) ÷ 12 = 72, the smallest number both 24 and 36 divide into evenly.
How is GCD used to simplify a fraction?
Divide the numerator and denominator by their GCD to reduce a fraction to lowest terms - for example, 24/36 shares a GCD of 12, so dividing both by 12 gives the simplified fraction 2/3. See the Fraction Calculator for simplifying fractions directly.
Can this find the GCD or LCM of more than two numbers?
This calculator computes GCD and LCM for two numbers at a time. For three or more numbers, apply the calculation pairwise - find the GCD or LCM of the first two, then combine that result with the next number, repeating until all values are included.
What if the two numbers share no common factors besides 1?
Then their GCD is 1 (they're called coprime), and their LCM is simply the product of the two numbers - for example, GCD(8, 9) = 1 and LCM(8, 9) = 72.
What's the GCD and LCM of two identical numbers, like 15 and 15?
Both the GCD and LCM equal that number itself - GCD(15, 15) = 15 and LCM(15, 15) = 15, since a number always divides itself evenly.
Is a 'GCF' the same as a 'GCD'?
Yes - 'greatest common factor' (GCF) and 'greatest common divisor' (GCD) are two names for the same value: the largest number that divides evenly into both inputs.