Least Common Multiple Calculator

Find the least common multiple of two or more numbers

This least common multiple calculator is built for one job: given a set of whole numbers, find the smallest positive number that each of them divides into exactly. That single number is the LCM. People usually search for this when they need a shared timing point (like events repeating every N days), when they want a common denominator to add or compare fractions, or when they are simplifying a problem that involves repeating patterns.

To use it, type your numbers as a comma separated list and press Calculate. The tool accepts two or more values. You will get the LCM first, because that is the decision you came for. Under that, you get supporting information that helps you sanity check the result: the cleaned list of numbers that were used, the count of numbers, and the greatest common divisor (GCD) of the set. The GCD is not the main output, but it is useful context because LCM and GCD are linked: when numbers share larger common factors, the LCM often grows more slowly than you expect.

What the result means in practical terms is simple. If you are matching schedules, the LCM is the next time everything lines up again. If you are working with fractions, the LCM of the denominators is a common denominator that always works. It may not always be the smallest possible common denominator if you have already reduced your fractions, so if you are using this for fractions, reduce each fraction first, then run the denominators through this calculator.

Assumptions and how to use this calculator

• This calculator is for whole numbers only. Decimals and fractions are not supported because LCM is defined in a clean way for integers.
• All values must be greater than zero. Zero does not have a practical LCM in the usual sense, so the tool will reject it.
• Very large numbers can overflow safe integer math in browsers. If the computed LCM becomes too large to be reliable, the tool will warn you.
• Separators can be commas or spaces. The calculator will ignore extra spaces and multiple separators.
• If you are using LCM for fractions, reduce your fractions first so you are not feeding inflated denominators into the tool.

Common questions

What is the difference between LCM and GCD?

The GCD is the largest number that divides each input exactly. The LCM is the smallest positive number that every input divides exactly. They describe opposite ends of the same “shared factors” idea: GCD looks for the biggest shared divisor, while LCM looks for the smallest shared multiple.

Why does the calculator reject decimals or negative numbers?

For everyday use, LCM is meant for positive integers. Decimals and negatives make the idea of a “smallest common multiple” either ambiguous or dependent on how you represent the values. If you need LCM-like behavior for rational numbers, convert them into reduced fractions first and use the denominators (and handle sign separately).

How many numbers can I enter?

You can enter multiple numbers, but more inputs increases the chance that the LCM grows extremely large. In real use, most people need 2 to 6 numbers. If your result becomes too large for safe integer math, the calculator will tell you instead of giving a misleading number.

My LCM looks huge. Is that normal?

Yes. If your numbers do not share factors (for example, they are mostly prime relative to each other), the LCM can be close to the product of the numbers. If they share factors, the LCM is smaller because overlapping factors are counted once.

What is the fastest way to get a correct answer for fractions?

Reduce each fraction first. Then enter only the denominators of the reduced fractions. The LCM you get is a clean common denominator. After that, scale each fraction up to that denominator using multiplication, not division, so you avoid rounding errors.