How to Find the Greatest Common Factor (GCF)

Math homework, quizzes and tests will ask students to find the greatest common factor. This term may also be abbreviated by GCF. The greatest common factor is the largest factor that will divide two (or more) numbers. Finding the greatest common factor is a common practice when working with fractions, but it is also used in other areas of math. Here is an easy step by step guide to help you find the greatest common factor.

Difficulty: Easy

Instructions

1. Begin by listing the prime factors of the first number. Factors are the numbers that are multiplied together to create a certain number. A prime factor means that it can only be divided by the number 1 and itself. For example, the numbers 2 and 3 are both prime factors.

2. Find the prime factors of the other number in question. You should be finding whole numbers that do not have any decimals or fractions to be considered a common factor.

3. Now that you have all of the prime factors listed for each number, find the factors that are in both of your numbers and multiply them together. The result is your greatest common factor for the two numbers.