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LCM Calculator
Find the common ground.
Understand every step.
Find the least common multiple and GCF of your numbers.
Compare step-by-step methods, fractions, and common denominators.
Free to use No sign-up Works on your device
Let’s work it out
LEAST COMMON MULTIPLE
Exact result72
LCM(12, 18, 24) = 72
GCF / GCD 6
Exact integer math. Never a rounded guess.Limits & conventions
THE WHY BEHIND THE ANSWER
A little working. A lot of clarity.
Prime factorizationFollow along at your own pace.
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NOT JUST AN ANSWER
Explore the methods Make the math make sense.
See the connection
Turn abstract factors into building blocks, then explore where your multiples meet.
Small inputs. Big possibilities.
Explore fractions, find a common denominator, or work through a whole batch at once.
A QUICK REFRESHERWhat is the least
What is the least
common multiple?
The least common multiple (LCM) is the smallest positive number that is a multiple of every positive integer in your set.
Think of two repeating rhythms. The LCM is the first moment they meet again. It helps with fractions, repeating schedules, and finding common ground between numbers.
Get to know the LCMLET’S TAKE 4 AND 6
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The first number they shareLCM = 12
How do I find the LCM of three or more numbers?+
Combine the first two numbers, then combine that result with the next. Continue until every number is included. Or prime-factor every number and keep the greatest exponent of each prime. This calculator accepts up to 20 inputs.
What is the difference between LCM and GCF?+
The LCM is the smallest shared positive multiple. The greatest common factor (GCF), also called GCD or HCF, is the largest positive integer dividing every input. For 12 and 18, the LCM is 36 and the GCF is 6.
Can I enter zero or negative numbers?+
Yes. Negative integers are treated by their absolute values. If any input is zero, the LCM is zero by the computational convention used here. The GCD of all zeros is also zero.
Does it work with fractions and decimals?+
Choose Fractions to calculate the LCM of rational numbers, or switch to least common denominator to rewrite fractions over a shared denominator. Finite decimals are converted exactly; these are two different operations.
Are large-number answers exact?+
Yes. Integer arithmetic uses BigInt, not floating-point approximations. Inputs can contain up to 100 digits each. For large inputs, some teaching methods switch to Euclid and say so explicitly.
Are my calculations saved or sent anywhere?+
The app does not send your inputs to a server. History stays in the current tab unless you enable local saving. Sharing a calculation is an explicit action. Read the privacy details for hosting and shared-link caveats.
How to use this LCM calculator
- Choose Whole numbers and enter 2–20 integers separated by commas or spaces.
- Choose a method, then select Calculate LCM. The result includes the least common multiple, the GCF/GCD and the working.
- Compare methods or check that the result divides exactly by each non-zero input. Use Fractions for rational numbers or a least common denominator, Batch for separate lines, and Range for all integers from 1 to your chosen endpoint.
A quick example: 12 = 2² × 3 and 18 = 2 × 3². Keep each prime’s greatest power: LCM(12, 18) = 2² × 3² = 36. The greatest common factor is 6.
For positive integers, “lowest common multiple” and “least common multiple” mean the same thing. Learn how LCM and GCF differ, compare rational LCM and the least common denominator, or practice with LCM word problems.
LCM calculator examples: exact answers to try
Choose a worked example to load its inputs and method. Integer LCM, rational LCM and least common denominator are different operations; the table labels each one.
| Calculation | Exact answer | Try the working |
|---|---|---|
| LCM of 12 and 18 | 36 | Prime factorization |
| LCM of 8, 12 and 20 | 120 | Three-number working |
| LCM of 1 through 10 | 2520 | Range mode |
| Rational LCM of 1/2 and 3/4 | 3/2 | Fraction LCM |
| LCD of 1/2 and 3/4 | 4 | Common denominator |
| Batch: 12, 18; then 8, 12, 20 | 36; 120 | Two independent calculations |
Not sure where to start? Choose an LCM method, compare LCM, GCF, GCD and HCF, or explore large-integer examples. The calculator supports up to 100 digits per integer; teaching methods have separate limits.
Need Batch LCM for separate problems? Process up to 50 non-empty lines with 2–20 integers per line, within the input box's 50,000-character limit. Range mode covers every integer from 1 to n, not just the two endpoints. For finite decimals, see an exact decimal LCM example.
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Different numbers. One common ground.
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