Question: how many cups in 1 box powdered sugar?
Answer: Powdered sugar right out of the box or the plastic bag weighs 4 1/2 ounces per cup, so a 1-pound box (or 16 ounces) contains about 3 1/2 cups of powdered sugar. If a recipe calls for sifted powdered sugar, weigh out 4 ounces of sifted powdered sugar to equal 1 dry measuring cup.