About the GCD & LCM Calculator
The greatest common divisor (GCD, also called HCF or GCF) is the largest number that divides all the numbers; the least common multiple (LCM) is the smallest number they all divide into. HCF simplifies fractions and shares things into equal groups; LCM finds common denominators and when repeating events line up.
Enter two or more whole numbers. The calculator shows Euclid’s algorithm (divide, keep the remainder, repeat), the prime factorisation of each number, and both answers, with the check GCD × LCM = a × b for two numbers.