LCM Calculator Find the Least Common Multiple Easily
Need the LCM of two or more numbers fast? Type your numbers into the calculator and get the answer in one click. Below, you will also learn how LCM works, so you can solve it by hand too.
What Is LCM?
LCM stands for Least Common Multiple. It is the smallest number that can be divided evenly by all the numbers you are working with.
Take 4 and 6:
- Multiples of 4: 4, 8, 12, 16, 20, 24…
- Multiples of 6: 6, 12, 18, 24, 30…
The common multiples are 12, 24, and so on. The smallest one is 12, so LCM of 4 and 6 = 12.
How to Find LCM
There are two easy methods.
1. Listing multiples
Write the multiples of each number until you find the first match. This works well for small numbers.
2. Prime factorization
Break each number into prime factors, then multiply the highest power of every prime.
Example: LCM of 12 and 18
- 12 = 2² × 3
- 18 = 2 × 3²
- Take the highest powers: 2² × 3² = 4 × 9 = 36
LCM Formula
For two numbers:
LCM(a, b) = (a × b) ÷ GCD(a, b)
Example: a = 12, b = 18
- GCD of 12 and 18 = 6
- LCM = (12 × 18) ÷ 6 = 216 ÷ 6 = 36
More Solved Examples
| Numbers | LCM |
|---|---|
| 5 and 10 | 10 |
| 8 and 12 | 24 |
| 15 and 20 | 60 |
| 4, 6 and 8 | 24 |
Practical Example
Two buses leave a stop at 8:00 AM. One comes back every 12 minutes, the other every 18 minutes. When will they be at the stop together again?
LCM of 12 and 18 = 36. So both buses meet again after 36 minutes, at 8:36 AM.
LCM is also used to add fractions. To add 1/4 + 1/6, find the LCM of 4 and 6, which is 12. Then 3/12 + 2/12 = 5/12.
How to Use the LCM Calculator
- Enter two or more numbers (separate them with commas).
- Click the “Calculate” button.
- See the LCM instantly.
FAQs
Can LCM be smaller than the numbers?
No. LCM is always equal to or bigger than the largest number.
What is the LCM of two prime numbers?
Just multiply them. LCM of 3 and 7 = 21.
