To find the greatest common factor and least common multiple, enter two whole numbers into the GCF / LCM Calculator. The GCF is the largest number that divides both, and the LCM is the smallest number both divide into.
Follow along with the free GCF / LCM Calculator, which runs in your browser, or browse more tools in this category.
How to use the GCF / LCM Calculator
- Enter two whole numbers.
- Read the GCF and LCM.
- Use the GCF to simplify fractions and the LCM to find common denominators.
- Try another pair.
Worked example
For 12 and 18 the GCF is 6 and the LCM is 36. You can check it: 12 x 18 = 216, and 6 x 36 = 216.
Tips and common mistakes
- The product of two numbers equals their GCF times their LCM.
- If the GCF is 1 the numbers are coprime.
- Use the LCM as the common denominator when adding fractions.
Frequently asked questions
What is the GCF used for?
Simplifying fractions and splitting things into equal groups.
What is the LCM used for?
Finding a common denominator or the next time two cycles line up.
Does it accept decimals?
It works with whole numbers.