LCM Calculator
Find the least common multiple of two or more numbers.
Try an example
36
About this calculator
How This LCM Calculator Works
Enter two or more numbers, and the calculator returns their least common multiple — the smallest positive number that every one of them divides into evenly.
Worked Example
The LCM of 15 and 20 is 60 — the smallest number both 15 and 20 divide into with no remainder.
Where LCM Comes Up
The most common use is finding a common denominator when adding, subtracting, or comparing fractions with different denominators. It's also useful for scheduling problems — like figuring out when two recurring events (buses running every 15 and 20 minutes, say) will next line up at the same time.
Worked example
The least common multiple of 12 and 18 is 36 — the smallest number both 12 and 18 divide into evenly.
Frequently asked questions
How is the LCM calculated?
This calculator uses the relationship LCM(a, b) = (a × b) ÷ GCF(a, b), extended pairwise across every number you enter.
What's the LCM used for?
Most commonly for adding or comparing fractions with different denominators — the LCM of the denominators gives the smallest common denominator to convert them to.
Can I find the LCM of more than two numbers?
Yes — add as many numbers as you need; the calculator finds the LCM pairwise across the whole list.
What's the difference between LCM and GCF?
LCM is the smallest number every input divides into; GCF (greatest common factor) is the largest number that divides every input evenly — opposite ends of the same relationship.