Greatest Common Factor Calculator:
Tool to Find GCF of Numbers

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This free online greatest common factor tool will find the GCF of 2, 3, or 4 numbers at once with the click of a button.

Plus, in addition to displaying the GCF, the calculator will also display the GCF divisors and all factors for the numbers entered.

Also, if you would ever like to save some time when attempting to find the least common multiple (LCM) for up to 4 numbers, be sure to check out my Least Common Multiple Calculator.

What are Factors?

The factors of a number is the set of all non-zero numbers that divide into the number evenly. For example, the factors of the number 12 would be as follows:

What are Common Factors?

Common factors occur when two or more numbers share one or more of the same factors. For example, the numbers 12 and 20 have the following factors, with the common factors appearing in orange:

What is a Greatest Common Factor?

The greatest common factor (A.K.A: GCF, Greatest Common Divisor, GCD) is the highest factor that two or more numbers share. Referring back to the numbers 12 and 20, the GCF would be 4 based on the following set of common factors:

How is Finding the Greatest Common Factor Useful?

The most common use of finding the GCF is for reducing or simplifying fractions, which we will cover on the various fraction calculator pages.

With that, let's use the Greatest Common Factor Calculator to find the GCF of up to 4 different numbers.

Greatest Common Factor Calculator
Instructions: Enter at least two numbers to find the GCF for and then click the "Find the Greatest Common Factor" button. Mouse over the blue question marks for a further explanation of each entry field. More in-depth explanations can be found in the glossary of terms located beneath the Greatest Common Factor Calculator.
1st number (#):
2nd number (#):
3rd number (optional #):
4th number (optional #):
Greatest common factor:
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Greatest Common Factor Calculator Glossary of Terms

Factors: The set of all non-zero numbers that will divide evenly into a given number.

Common factors: Factors that are shared by two or more given numbers.

1st number: Enter the first of the numbers to find the highest common factor for.

2nd number: Enter the second of the numbers to find the largest common factor for.

3rd number: Enter the optional 3rd of the numbers to find the greatest common factor for. In order to include the 3rd number, the 1st and 2nd numbers are required.

4th number: Enter the optional 4th of the numbers to find the GCF for. In order to include the 4th number, the 1st, 2nd, and 3rd numbers are required.

Greatest common factor: This is the GCF for the numbers you entered. If the result is 1, it means that your entries don't have any factors in common other than the number 1 -- meaning no reduction or simplification is possible.

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