LCM calculator
Enter two or more whole numbers and see their least common multiple, the smallest number that all of them divide into, with the steps.
Whole numbers, separated by a semicolon, comma or space.
Fill in the fields; the answer appears here straight away.
How it's worked out
How it works
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Enter the values
Type the numbers or the formula. Decimals may use a point or a comma. No idea? Click Fill in an example.
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Instant answer
The answer appears as you type, with the most important intermediate values.
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See the working
Under "How it's worked out" you see the steps, handy for checking your own calculation.
What is the LCM?
The least common multiple (LCM) is the smallest positive number that is a multiple of each of your numbers. The LCM of 4, 6 and 15 is 60: 60 is in the 4 times table, the 6 times table and the 15 times table, and no smaller number is.
How it is calculated
For two numbers, LCM(a, b) = a × b ÷ GCD(a, b). For more numbers, repeat it: LCM(4, 6) = 12, then LCM(12, 15) = 12 × 15 ÷ 3 = 60. Using the GCD keeps the numbers small, so it works for large inputs too.
Where you need it
When adding fractions with different denominators: for 1/4 + 1/6, the LCM 12 is the common denominator. It also tells you when repeating events line up, such as two buses leaving every 4 and 6 minutes, which leave together again after 12 minutes. See also add fractions.
Frequently asked questions
Is the LCM calculator free?
Yes. The LCM calculator is completely free, with no account, sign-up or usage limit.
How accurate is the result?
The tool calculates with your browser's number precision. For important calculations, always double-check what you entered.
Does it work on my phone?
Yes. The tool works in any modern browser on a phone, tablet or computer.