GCF & LCM Calculator
Find the greatest common factor and least common multiple of two or more numbers, with full prime factorization.
Your Numbers
| Number | Prime Factorization |
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How This Calculator Works
Enter two or more positive whole numbers — add as many as you need. The GCF (Greatest Common Factor), also called the GCD, is the largest number that divides evenly into all of them. The LCM (Least Common Multiple) is the smallest number that all of them divide into evenly. Both are computed for the full list at once, and each number's prime factorization is shown alongside the result.
Frequently Asked Questions
The GCF, also called the GCD (Greatest Common Divisor), is the largest number that divides evenly into every number in the list. For example, the GCF of 12 and 18 is 6.
The LCM is the smallest number that every number in the list divides into evenly. For example, the LCM of 4 and 6 is 12.
Break each number down into its prime factors, then multiply together the prime factors common to all the numbers, using the lowest power each appears with. This calculator shows the full prime factorization of every number you enter.
GCF is used to simplify fractions to lowest terms. LCM is used to find a common denominator when adding or subtracting fractions, and in scheduling problems like figuring out when two repeating events will next line up.