LCM of Three Numbers Calculator

Enter three whole numbers to find their least common multiple, with the steps shown.

Finding the LCM of three numbers

The easiest way is prime factorization. Break each number into primes, then multiply the highest power of each prime.

6 = 2 × 3
10 = 2 × 5
15 = 3 × 5
LCM = 2 × 3 × 5 = 30

You can also work in pairs. LCM(6, 10) = 30, and then LCM(30, 15) = 30. The order you pick does not change the answer.

Common mistake

Do not multiply all three numbers together and call it done. 6 × 10 × 15 = 900, but the LCM is only 30. Shared factors would be counted more than once.