GCF and LCM Calculator
Find the GCF and LCM of a list of numbers, with the prime factors shown.
What they mean
The greatest common factor (also called the greatest common divisor) is the largest number that divides every number in your list. The least common multiple is the smallest number that every number in your list divides into.
How they are found
Write each number as a product of primes. The GCF uses the lowest power of each prime that all numbers share. The LCM uses the highest power of every prime that appears in any number.
Example
12 = 2² × 3, 18 = 2 × 3² and 30 = 2 × 3 × 5. The GCF is 2 × 3 = 6. The LCM is 2² × 3² × 5 = 180.
The GCF simplifies fractions: divide the top and bottom by it. The LCM finds a common denominator when adding fractions.
Frequently asked questions
What if the numbers share no factors?
Then the GCF is 1, and the numbers are called coprime. The LCM is then their product.
Can I use decimals?
No, only whole numbers. For fractions, use the fraction calculator.
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