LCM Calculator
Enter two or more whole numbers to find their least common multiple. The greatest common factor is shown as well.
This result is an estimate only. Double-check important figures before relying on them.
How it is calculated
- LCM(a, b) = a ÷ GCF(a, b) × b
- For more numbers, take the LCM of the first two, then of that result and the next number, and so on
- The GCF is found with the Euclidean method
To find the largest common divisor, use the GCF calculator. For other number work, use the scientific calculator.
Worked example
The numbers 4, 6 and 10:
- GCF(4, 6) = 2, so LCM(4, 6) = 4 ÷ 2 × 6 = 12
- GCF(12, 10) = 2, so LCM(12, 10) = 12 ÷ 2 × 10 = 60
Why your number may differ
The calculator accepts whole numbers from 1 up to one trillion, and at most 20 numbers. The result is exact even when it is very large.
Frequently asked questions
What is the least common multiple?
It is the smallest positive number that every number in the list divides into evenly. For 4 and 6 it is 12.
How do I find the LCM?
For two numbers, LCM = a × b ÷ GCF(a, b). For more numbers, find the LCM of the first two, then of that result and the next number, and so on.
What is it used for?
Adding fractions with different denominators, and working out when repeating events line up, such as buses leaving every 4 and 6 minutes.