3 1/2 cups Powdered sugar directly out of the box or the plastic bag weighs 4 1/2 ounces per cup, thus a 1-pound box (or 16 ounces) holds around 3 1/2 cups of powdered sugar. If a recipe asks for sifted powdered sugar, weigh out 4 ounces of sifted powdered sugar to equal 1 dry measuring cup.
Do you sift powdered sugar before or after you measure it?
How Many Cups in a Pound?
Powdered sugar, also known as confectioner’s sugar, is white sugar that has been crushed into a fine powder so that it dissolves easily; it is typically used to make icings and frostings or as a garnish for baked products. About three percent of powdered sugar is cornstarch, which helps absorb moisture and avoid caking.