Find the least common multiple of two whole numbers.
Try an example
Load a ready-made sample into this tool and run it. Every result you see is calculated live by the tool itself — nothing here is a pre-written answer.
Sample: a: 12; b: 18
How to Use
- Enter two whole numbers.
- Click Run.
- Read the smallest number both divide into.
What this LCM calculator does
This LCM calculator finds the least common multiple of two whole numbers — the smallest number that both of them divide into exactly. Enter the pair and it returns the LCM straight away. The value is the standard tool for finding common denominators, and for working out when two repeating cycles or patterns next coincide with each other. No long lists of multiples need to be written out to reach the answer.
How the LCM is found
The standard shortcut uses the greatest common divisor: LCM = (first number × second number) ÷ GCD of the two. For example, 4 and 6 have a GCD of 2, so their LCM is 24 ÷ 2 = 12 — the first multiple that appears in both numbers’ lists of multiples.
Good to know
Zero has no meaningful least common multiple with another number, so entering zero produces an error rather than a result. The calculator works with a pair of whole numbers at a time; for three numbers, combine two first, then find the LCM of that result together with the third.
Frequently asked questions
What is the LCM used for?
Common denominators: the LCM of two denominators is the smallest one both fractions can be rewritten over. It also answers timing questions, like when two repeating events on different cycles next coincide.
Is the LCM the same as the LCD?
Closely related. The least common denominator in fraction work is simply the LCM of the denominators, so the value returned for two denominators is exactly the LCD used to add those fractions.
Can the LCM be one of the two numbers?
Yes. When one number is a multiple of the other — 3 and 12, for example — the larger number is itself the least common multiple, since the smaller divides into it exactly.
How to use LCM Calculator
- Enter two whole numbers.
- Click Run.
- Read the smallest number both divide into.
Limitations
Zero has no meaningful least common multiple with another number and is rejected with an error.