How to use the LCM calculator
Type 2 to 10 whole numbers separated by commas or spaces and press Find LCM. The working shows listed multiples, prime factors and – for two numbers – the GCF shortcut.
What is the least common multiple?
The least common multiple (LCM) is the smallest number that every number in the list divides into exactly. It is used to find common denominators and to work out when repeating events line up.
Three ways to find the LCM
- List multiples: 4: 4, 8, 12; 6: 6, 12 → LCM 12.
- Prime factors: take every prime with its highest power. 4 = 2², 6 = 2 × 3 → LCM = 2² × 3 = 12.
- Using the GCF (two numbers): LCM = a × b ÷ GCF(a, b) = 4 × 6 ÷ 2 = 12.
Frequently asked questions
What is the LCM of 4 and 6?
12 – the smallest number that both 4 and 6 divide into.
How are LCM and GCF related?
For two numbers, LCM × GCF = the product of the numbers. So LCM = a × b ÷ GCF.
How do you find the LCM of three numbers?
Use prime factors (highest power of every prime), or work in pairs: LCM(a, b, c) = LCM(LCM(a, b), c).
What is the LCM used for?
Finding a common denominator for fractions, and problems like when two buses that leave every 12 and 18 minutes next leave together (every 36 minutes).