GCF & LCM Calculator (Free Step-by-Step Tool)

Use this free GCF and LCM calculator to find the greatest common factor and least common multiple of two or more whole numbers. Enter your numbers and you’ll get both results with the full prime-factorization steps.

How to use the GCF & LCM calculator

1. Type two or more whole numbers, separated by commas or spaces.
2. Press Calculate.
3. Read the GCF, the LCM, and the step-by-step prime factorizations.

GCF vs. LCM

The GCF (greatest common factor) is the largest number that divides all of your numbers. The LCM (least common multiple) is the smallest number that all of your numbers divide into. The tool finds both from the prime factorizations.

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Frequently asked questions

How do you find the GCF using prime factorization?

Write each number as a product of primes, then multiply the primes they share, using the lowest power of each. The calculator shows every step.

How do you find the LCM?

Take every prime that appears in any number, using the highest power of each, and multiply them. The result is the least common multiple.

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Can it handle more than two numbers?

Yes — enter as many whole numbers as you like, separated by commas or spaces.

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Read the full lesson: learn the method step by step.

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