What is the LCM used for?

LCM is commonly used to find a common denominator when adding or subtracting fractions with different denominators.

How is LCM related to the LCD used with fractions?

The least common denominator (LCD) of a set of fractions is exactly the LCM of their denominators — see the LCD Calculator for a version framed specifically around fractions.

LCM Calculator

Find the least common multiple (LCM) of two or more numbers — the smallest number that all of them divide into evenly.

Numbers (comma or space separated)

Least Common Multiple

How It Works

Using the greatest common factor

The LCM of two numbers can be found from their greatest common factor (GCF): LCM = (a × b) ÷ GCF(a, b). For more than two numbers, this is applied repeatedly.

Example Calculation

The LCM of 4 and 6 is 12 — the smallest number both 4 and 6 divide into evenly.

Common Mistakes

Confusing LCM with GCF — LCM is the smallest shared multiple (bigger than or equal to the largest input), while GCF is the largest shared factor (smaller than or equal to the smallest input).
Multiplying the numbers together directly instead of dividing out their common factor first, which overstates the true LCM.

Frequently Asked Questions

What is the LCM used for?: LCM is commonly used to find a common denominator when adding or subtracting fractions with different denominators.
How is LCM related to the LCD used with fractions?: The least common denominator (LCD) of a set of fractions is exactly the LCM of their denominators — see the LCD Calculator for a version framed specifically around fractions.