LCM Calculator 2026
Instantly find the Lowest Common Multiple of up to six numbers. Get full prime factorisation working shown step by step — perfect for maths homework, fractions, and scheduling problems.
Enter Your Numbers
Add between 2 and 6 positive integers — leave optional fields blank
Enter whole numbers only (integers ≥ 1). Decimals and negatives are not supported.
Prime factorisation works for any size of number. Listing multiples is clearer for small numbers.
LCM Result
Lowest Common Multiple with full working
Enter at least two positive whole numbers above, then click Find the LCM to see your result and step-by-step working.
Common LCM Examples
Frequently needed LCM values for pairs of numbers. Use these to check your own working or as a quick lookup for fractions with common denominators.
| Numbers | LCM | GCF / HCF | Common Application |
|---|---|---|---|
| 2 and 3 | 6 | 1 | Fractions: ½ + ⅓ |
| 4 and 6 | 12 | 2 | Fractions: ¼ + ⅙ |
| 6 and 9 | 18 | 3 | Gear / cycle ratios |
| 8 and 12 | 24 | 4 | Time intervals |
| 10 and 15 | 30 | 5 | Scheduling events |
| 12 and 18 | 36 | 6 | Fractions: 1/12 + 1/18 |
| 15 and 20 | 60 | 5 | Clock problems |
| 24 and 36 | 72 | 12 | Engineering cycles |
LCM FAQ
Everything you need to know about finding the Lowest Common Multiple, from the basics to real-world uses.
The Lowest Common Multiple (LCM), also called the Least Common Multiple, is the smallest positive integer that is divisible by all numbers in a given set. For example, the LCM of 4 and 6 is 12, because 12 is the smallest number that both 4 and 6 divide into evenly.
To find the LCM using prime factorisation: (1) Break each number down into its prime factors. (2) List all the unique prime factors across all numbers. (3) For each prime factor, take the highest power that appears in any of the factorisations. (4) Multiply these highest powers together — the result is the LCM.
The LCM (Lowest Common Multiple) is the smallest number that all given numbers divide into, whereas the HCF (Highest Common Factor), also called GCF, is the largest number that divides evenly into all given numbers. They are related by the formula: LCM(a, b) × HCF(a, b) = a × b.
The LCM is used when adding or subtracting fractions with different denominators (to find a common denominator), scheduling repeating events that recur at different intervals, calculating gear ratios, and solving problems involving periodic cycles in engineering and computing.
Yes. To find the LCM of more than two numbers, calculate the LCM of the first two numbers, then find the LCM of that result with the third number, and continue this process for every additional number. Our calculator handles up to six numbers simultaneously.