LCM Calculator
Free LCM calculator: enter two whole numbers to get their least common multiple instantly - great for fractions, scheduling and math homework.
About this tool
The least common multiple is the smallest number that both of your numbers divide into evenly. The LCM of 12 and 18 is 36 - the first number appearing in both times tables. It is the secret ingredient for adding fractions with different denominators.
To add 5/12 + 7/18, you need a common denominator: the LCM, 36. Rewrite as 15/36 + 14/36 = 29/36. This calculator finds that magic number for any pair, instantly.
How to use
Enter two whole numbers (1 or larger) and press Find LCM.
The least common multiple appears immediately. Use it to find common denominators for fractions, sync up repeating schedules (two buses every 12 and 18 minutes meet every 36), or check number-theory homework.
The math behind it
LCM(a, b) = |a x b| / GCF(a, b). Computing it through the greatest common factor (Euclid's algorithm) keeps the numbers small and exact, avoiding the overflow that multiplying first could cause.
Example: GCF(12, 18) = 6, so LCM = (12 x 18) / 6 = 216 / 6 = 36.
Frequently asked questions
When do I need the LCM in real life?
What is the difference between LCM and GCF?
Can the LCM be smaller than both numbers?
Related tools
💬 Comments
Have a question about this page, or an idea to make it better? Share it below — your feedback helps everyone who uses this site.