A third cup contains around 2.6 ounces. Multiply the cup measurement by 8, which is the amount of fluid ounces in 1 cup, to convert cups to ounces. One-third is equal to 0.33 ounces, one-half is equal to 0.5 ounces, one-fourth is equal to 0.25 ounces, and one-eighth is equal to 0.125 ounces.
Depending on what is being measured, the exact number of ounces in a cup can vary. Dry components, like flour or sugar, typically weigh less per ounce than solids and heavier liquids, like butter or honey. One-third cup of brown sugar is equivalent to 2.58 ounces, and one-third cup of honey is equivalent to 4 ounces. The weight of one-third cup of all-purpose flour is 1.5 ounces.