LCM Calculator

Calculate the least common multiple (LCM) of two whole numbers.

  • Free to use
  • No registration required
  • Works on all devices
Last updated
12-09-2026
Enter two whole numbers to calculate their least common multiple (LCM) and greatest common factor (GCF).

Your result

12

Least common multiple

Greatest common factor2

AI explanation

Formula

LCM = (a × b) / GCF, where GCF is computed via the Euclidean algorithm

Worked example

4 and 6

Worked example: 4 and 6
FieldValue
First number4
Second number6
Least common multiple12
Greatest common factor2

Assumptions

  • Both numbers must be positive whole numbers.

Frequently asked questions

What is the least common multiple?

It's the smallest positive whole number that both input numbers divide into evenly — the smallest number that's a multiple of both.

How is LCM calculated?

LCM = (a × b) / GCF, where GCF is the greatest common factor of the two numbers, computed via the Euclidean algorithm.

What is LCM used for?

LCM is commonly used to find a common denominator when adding or subtracting fractions, and in scheduling problems where events repeat at different intervals.

Related calculators

GCF CalculatorFactorial Calculator

Related articles

Mathematics1 min read

How to Find the Least Common Multiple of Two Numbers

The least common multiple (LCM) of two numbers is the product of the two numbers divided by their greatest common factor — a shortcut that avoids listing out multiples one by one.

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Mathematics1 min read

How GCF and LCM Are Related, and Why Simplifying Fractions Uses GCF

GCF and LCM are two sides of the same calculation — the LCM formula is built directly from the GCF — and each one solves a different fraction problem: GCF simplifies a single fraction, while LCM finds a common denominator to add two fractions together.

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