AI Calculator Tool

Menu

Free Online GCF Calculator

Type two or more whole numbers separated by commas. You get the greatest common factor—the largest number that divides every value evenly.

The greatest common factor (GCF) is the largest whole number that divides every value in your list. Also called GCD or HCF.

Try an example

How the GCF calculator works

The greatest common factor (GCF), also called GCD or HCF, is the biggest whole number that divides each number in your list with no remainder. It is the number you use to reduce fractions: divide the top and bottom by the GCF of numerator and denominator.

For small lists you can list factors by hand. For longer sets or bigger numbers, this tool is faster and less error-prone.

Worked examples

Real problems you might enter in the calculator above, with short walkthroughs.

  • GCF of 12 and 18

    6 is the largest number that divides both 12 and 18. So 12/18 simplifies to 2/3.

    Numbers1218GCF6

  • GCF of three numbers

    12 divides 24, 36, and 60 evenly. No larger number does.

    Numbers243660GCF12

  • Relatively prime pair

    When the only shared factor is 1, the numbers are coprime and the fraction 15/28 is already in lowest terms.

    Numbers1528GCF1

  • Simplifying 18/24

    Divide numerator and denominator by 6: 18/24 becomes 3/4.

    Numbers1824GCF6

Frequently asked questions about the gCF Calculator

  • What is the GCF?

    The greatest common factor is the largest whole number that divides every number in your list with no remainder.

  • Is GCF the same as GCD?

    Yes for positive integers. GCD (greatest common divisor) and GCF mean the same thing.

  • How do I use GCF to simplify a fraction?

    Divide the numerator and denominator by their GCF. Example: 12 and 18 have GCF 6, so 12/18 = 2/3.

  • Can I enter more than two numbers?

    Yes. Enter comma-separated values such as 12, 18, 24 and the calculator finds the GCF of the whole set.