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LCM calculator

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This calculator computes LCM of two or more numbers using five methods: the division method, listing multiples, prime factors, ladder method and the LCM formula. For each method, the calculator shows a detailed step-by-step explanation.

Least Common Multiple (LCM) Calculator
five methods each with its own steps
help ↓↓ examples ↓↓
12 20
15 35 14
Prime factors method (default)
Division method
Listing multiples method
Ladder method
LCM formulae
working...
examples:
example 1:ex 1:
Find the lowest number which is divisible by 12 and 15?
example 2:ex 2:
Find the LCM of 15, 140 and 32 using prime factorization method.
example 3:ex 3:
Find the least common multiple of 18, 15, 96 and 102 using ladder method.
example 4:ex 4:
Find the least common multiple of 204 and 315 using LCM formulae.
Find more worked-out examples in the database of solved problems..

What is Least Common Multiple?

The least common multiple (LCM) is the smallest number that is divisible by all given numbers. For example, LCM(8, 6) = 24, because 24 is divisible by 8 and it is divisible by 6, and it is the smallest such number.

Find LCM by listing multiples

Example: find LCM of 8 and 6 by listing multiples.

Step 1: The first few multiples of 6 and 8 are:

Multiples of 6: 6, 12, 18, 24, 30

Multiples of 8: 8, 16, 24, 32, 40

Step 2: LCM is the smallest numbers that appears in both lists:

LCM (6, 8) = 24

Note:This method is unsuitable for numbers that are greater than 20.

Find LCM using prime factors

Example: Find the LCM of 8, 12 and 30.

Step 1: Prime factorizations of given numbers are:

8 = 2 · 2 · 2

12 = 2 · 2 · 3

30 = 2 · 3 · 5

Step 2: Match primes vertically

8 = 2 · 2 · 2    
12 = 2 · 2 ·   3  
30 = 2 ·     3 · 5

Step 3: Bring down numbers in each column and multiply to get LCM:

8 = 2 · 2 · 2    
12 = 2 · 2 ·   3  
30 = 2 ·     3 · 5
LCM = 2 · 2 · 2 · 3 · 5 = 120

Find LCM using the ladder method

Example: Find the LCM of 84 and 112, using Ladder method.

Step 1: Place the numbers inside the division bar:

84 112

Step 2: Divide both numbers by 2:

2 84 112
42 56

Step 3: Repeat Step 2 until you can no longer divide

2 84 112
2 42 56
7 21 28
  3 4

Step 4:LCM is a product of numbers into L shape.

2 84 112
2 42 56
7 21 28
  3 4

LCM = 2 · 2 · 7 · 3 · 4 = 336

Find LCM using division method

Example: find LCM of 18, 24 and 60 using the division method.

Step 1: Write the given numbers on a horizontal line.

18 24 60

Step 2: Divide numbers by the smallest prime number. If any number is not divisible by 2 write it down unchanged.

18 24 60
2 9 12 30
2 9 6 15
2 9 3 15

Step 3:Continue dividing by prime numbers 3, 5, 7... Stop when the last row contains only ones.

18 24 60
2 9 12 30
2 9 6 15
2 9 3 15
3 3 1 5
3 1 1 5
5 1 1 1

Step 4:Multiply the numbers in the first column to get LCM

LCM(18, 24, 60) = 2 · 2 · 2 · 3 · 3 · 5 = 360

LCM formulae

Example: find LCM of 48 and 60?

In this section we use formula

$$ \text{LCM(a,b)} = \dfrac{ a \cdot b }{ \text{GCD(a,b)} } $$

Since GCD(48, 60) = 12, we have:

$$ \text{LCM(48, 60)} = \dfrac{ 48 \cdot 60 }{ \text{GCD(48, 60)} } = \dfrac{2880}{12} = 240$$
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