The LCM Calculator

How to use a LCM Calculator in

This online least common multiple calculator simplifies finding the LCM of two or more numbers. It provides answers faster than using the manual method.

How to Find LCM

The LCM ( Least Common Multiple) is the smallest positive number that is evenly divisible by two or more numbers.  It is also known as the Lowest Common Multiple or the Least Common Divisor (LCD).

There are several LCM finder methods:

  1. Listing Multiples

  2. Prime Factorization

  3. Cake/Ladder Method

  4. Division Method

  5. Using the Greatest Common Factor GCF

  6. Venn Diagram

Let’s have a look at the two  most popular methods: listing multiples, and prime factorization.

Method 1: Listing Multiples

This LSM finder method involves listing the multiples of each number and identifying the smallest number common to all lists.

Example: Find LCM (8, 12, 20).

Multiples of 8

8, 16, 24, 32, 40, 48, 56, 64, 72, 80, 88, 96, 104, 112, 120

Multiples of 12

12, 24, 36, 48, 60, 72, 84, 96, 108, 120

Multiples of 20

20, 40, 60, 80, 100, 120

The smallest number available on all the lists is 


So, LCM(8, 12, 20) 


Method 2: Prime Factorization

Here are the steps you need to follow to use this lcm finder method:

  1. List the prime factors of each of the given numbers.

  2. Compile a list of the prime factors identified, repeating them as many times as they appear in any one of the numbers.

  3. Multiply these prime factors together to determine the LCM.

Example: Find LCM(20, 36):

Prime factorization of 20

2 × 2 × 5

Prime factorization of 36

2 × 2 × 3 × 3

List prime factors as often as they occur most frequently

2 (twice), 3 (twice), 5 (once)

Multiply these prime factors together

2 × 2 × 3 × 3 × 5 = 180

The LCM(20, 36) is 


You do not have to do the calculations yourself. Use the Mathmaster's least common multiple calculator to make your calculations simpler. Just input the numbers you want to analyze separated by commas or spaces, then press calculate.


  1. Is the LCM the same as the least common denominator (LCD) used in fractions?

No, the LCM is used to find the common multiple of integers, while the LCD is used in fractions to make addition or subtraction easier. However, the LCM can be used to find the LCD.

  1. How does the Least Common Multiple calculator work with multiple methods?

The MathMaster LCM calculator uses hidden algorithms in the background. It does not allow you to choose a method.

  1. How can I calculate the LCM of decimal numbers?

Convert the decimal numbers into integers by moving the decimal point to the right. Find the LCM of the integers and move the decimal point back to its original position.