To simplify a fraction, divide both the top number, the numerator, and the bottom number, the denominator, by the greatest common factor. Simplifying a fraction is reducing it to its lowest form.

**Find the greatest common factor**Make a list of the factors of the numerator. A factor is a number that is able to be divided into another number. Make a separate list of the factors of the denominator. Find the highest common number between the two lists. This is the greatest common factor. For example, in the fraction 6/18, the numerator's factors would be: 1, 2, 3 and 6. The denominator's factors would be 1, 2, 3, 6, 9 and 18. The highest common number between the two lists is 6. This is the greatest common factor.

**Divide the numerator by the greatest common factor**Divide the numerator by the greatest common factor found in the lists. In this example, 6 divided by 6 is 1.

**Divide the denominator by the greatest common factor**Divide denominator by the greatest common factor found in the lists. Dividing by the same number keeps the value of the fraction the same. In this example, 18 divided by 6 is 3.

**Re-write the fraction**Use the new values of the numerator and the denominator and re-write the fraction. In this example, the fraction is reduced from 6/18 to 1/3.