GCF and LCM, with the working shown — free, no sign-up
The greatest common factor (GCF, also called GCD) is the largest number that divides both numbers evenly. The least common multiple (LCM) is the smallest number that both divide into evenly. This tool finds both using the Euclidean algorithm, shows every division step for free, and needs no account or app.
Frequently asked questions
How is the GCF calculated?
Using the Euclidean algorithm — repeatedly dividing the larger number by the smaller and keeping the remainder, until the remainder is 0. The last non-zero remainder is the GCF. It's the same method shown step by step below, not just the final answer.
How is the LCM calculated from the GCF?
LCM(a, b) = (a × b) ÷ GCF(a, b). Once you have the GCF, the LCM follows directly from that one formula.
Does this work for any two whole numbers?
Yes, for any two positive whole numbers. Enter them in either order — the result is the same.
Is this free with no sign-up?
Yes — completely free, runs in your browser, no account needed.