GCF and LCM Calculator
Find the greatest common factor and least common multiple of any numbers.
About the GCF and LCM Calculator
The greatest common factor (GCF, also called HCF) is the largest number that divides a set of numbers exactly; the least common multiple (LCM) is the smallest number they all divide into. The AlarmDaddy GCF and LCM Calculator finds both for two or more whole numbers at once — the two operations you need most when adding fractions or solving ratio problems.
Enter your numbers separated by commas and read the GCF and LCM instantly. It works with any count of numbers, not just two, so you can find the common factor of a whole list at once.
How to use this calculator
- 1Enter two or more whole numbers, separated by commas.
- 2Read the greatest common factor (GCF/HCF).
- 3Read the least common multiple (LCM).
The formula
The GCF is found with the Euclidean algorithm, repeatedly replacing the larger number with the remainder of dividing the two. The LCM uses the identity that the product of two numbers equals their GCF times their LCM, applied cumulatively across all the numbers.