LCM and GCF Calculator

The greatest common factor (GCF) is the largest positive integer that divides every number in the list. The least common multiple (LCM) is the smallest positive integer that every number in the list divides into. They are complementary: for two numbers a and b, a × b = GCF × LCM.

Only positive whole numbers are used. Anything that is zero, negative, decimal, or non-numeric is skipped, and the calculator shows how many entries it ignored so you can correct the list.

It applies the Euclidean algorithm pairwise across the list, repeatedly replacing the larger number with the remainder until one of them is zero. The LCM uses the identity LCM(a, b) = a × b ÷ GCF(a, b), extended across the list with reduce.