LCM Calculator
Find the least common multiple of two or more whole numbers.
What the LCM Calculator does
The least common multiple is the smallest number that every input divides into evenly. It is what you need to add fractions with different denominators, or to work out when repeating schedules coincide.
Formula
lcm(a, b) = |a × b| ÷ gcd(a, b)For more values, fold the pairwise LCM across the list
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Numbers | text | Yes | Separate values with commas, spaces or new lines. |
How to use it
- Enter Numbers.
- Select Calculate.
Worked example
Two buses leave every 4 and 6 minutes. When do they next leave together?
- Numbers
- 4, 6
lcm(4, 6) = 12, so every 12 minutes.
Reading the result
- The LCM is the common denominator you need to add fractions, and the point at which two repeating schedules next coincide.
- For any two numbers, GCD × LCM equals their product, which is a quick way to check either result.
Common mistakes
- Multiplying the numbers together and calling it the LCM. That only holds when they share no factors.
- Confusing it with the GCD. The LCM is at least as large as the largest input.
Frequently asked questions
How is LCM used with fractions?
The LCM of the denominators is the lowest common denominator, the smallest denominator you can rewrite both fractions over.