One pound of powdered sugar is approximately 3 3/4 cups when measured unsifted. The measurement of powdered sugar can vary slightly, with 1 pound ranging between 3 1/2 cups and 4 cups.
Powdered sugar is also known as confectioner's sugar or icing sugar. It is very fine and is made by grinding normal granular sugar into a fine powder. It is often mixed with cornstarch, wheat flour or calcium phosphate to improve its ability to flow. There are different levels of fineness in powdered sugar, which is why the amount of cups of powdered sugar in 1 pound can vary.