GCF & LCM Calculator 🔒 Your data never leaves your browser.
Find the greatest common factor and least common multiple of two or more numbers.
About this tool
This GCF and LCM calculator finds the greatest common factor and least common multiple of any list of positive whole numbers, right in your browser. Type two or more numbers separated by commas or spaces and both results update as you type. The GCF (also called the greatest common divisor) is the largest number that divides every one of your inputs evenly — it's the key step in simplifying a fraction down to its lowest terms. The LCM is the smallest number that every one of your inputs divides into evenly — it's what you need to find a common denominator when adding or subtracting fractions, or to work out when two repeating events (like buses on different schedules) next line up.
Unlike calculators that only handle a pair of numbers, this tool accepts any number of inputs — three, five, ten — and computes the GCF and LCM across all of them at once, using the same Euclidean-algorithm logic taught in arithmetic classes. Try the built-in sample (12, 18, 24) to see it in action: the GCF is 6 and the LCM is 72.
Frequently asked questions
Does this work with more than two numbers?
Yes — enter as many positive integers as you like, separated by commas or spaces, and both the GCF and LCM are computed across the entire set at once (using the standard trick of folding the pairwise GCF/LCM operation across the whole list). This is handy for things like finding a common denominator for three or more fractions at once, or the greatest common factor shared by an entire group of numbers.