Quick answer: The LCM of 4, 6 and 8 is 24: 4 = 2², 6 = 2 × 3 and 8 = 2³, so the LCM is 2³ × 3 = 24.
How it's calculated
Prime factor method: write each number as a product of primes, then multiply every prime that appears at its highest power.
GCF method for two numbers: lcm(a, b) = a × b ÷ gcf(a, b). For more numbers, take the LCM of the first two, then of that result and the next number.
The LCM of the denominators is the lowest common denominator used to add fractions in the fraction calculator. The GCF calculator shows the Euclid steps for the GCF.
Worked examples
- 4, 6 and 8: 2³ × 3 = 24
- 12 and 18: 12 × 18 ÷ 6 = 36
- 5 and 7: 5 × 7 ÷ 1 = 35
Frequently asked questions
What is the LCM used for?
Adding and subtracting fractions (the lowest common denominator) and timing questions, such as when two repeating events next happen together.
Is the LCM ever smaller than the numbers?
No. The LCM is at least as large as the largest number in the list.
What is the LCM of two coprime numbers?
Their product, because their GCF is 1: lcm(5, 7) = 35.
What is the LCM of 4, 6 and 8?
24, the smallest number all three go into.
How do I add fractions with the LCM?
Use the LCM of the bottoms as your common denominator. For 1/4 + 1/6 that's 12, so 3/12 + 2/12 = 5/12.
When will two repeating events line up again?
After the LCM of their cycles. Buses every 12 minutes and every 18 minutes leave together again 36 minutes later.