Do not mistake weight ounces with volume ounces when measuring powdered sugar. Know exactly how much you are purchasing. Everyone is aware that one cup equals eight ounces, right? In actuality, when measuring components for a recipe, 1 cup does not necessarily correspond to 8 ounces.
We know that 1 cup of water weighs 8 ounces, but because honey is more viscous than water, 1 cup of honey weighs 12 ounces. Powdered sugar directly from the box or plastic bag weighs 4 1/2 ounces per cup; therefore, a 1-pound box (or 16 ounces) provides approximately 3 1/2 cups of powdered sugar. If a recipe asks for powdered sugar, 4 ounces of powdered sugar will equal 1 dry measuring cup.
Powdered sugar becomes lighter and fluffier when sifted, so it occupies more space in the cup. 
How much does one cup of powdered sugar weigh?
SUGARS & LIQUID SWEETENERS –
| Granulated Sugar Light Brown Sugar Dark Brown Sugar | 1 cup = 200 g |
|---|---|
| ½ cup = 100 g | |
| 1⁄3 cup = 67 g | |
| ¼ cup = 50 g | |
| 2 Tbsp = 25 g | |
| Superfine sugar Caster sugar | 1 cup = 225 g |
| ½ cup = 115 g | |
| 1⁄3 cup = 70 g | |
| ¼ cup = 60 g | |
| 2 Tbsp = 30 g | |
| Icing sugar (Powdered sugar or Confectioners’ sugar) | 1 cup = 130 g |
| ½ cup = 65 g | |
| 1⁄3 cup = 45 g | |
| ¼ cup = 32 g | |
| Coconut palm sugar | 1 cup = 170 g |
table> Liquid Sweeteners
For cupcake frosting, you must apply a thicker layer of icing. The amount of frosting needed for 12 cupcakes is around 1 cup.
How many cups of frosting are in a tub?
One 4-pound container makes eight cups of frosting, sufficient to ice two 8-inch round cakes with two layers each, three 9-by-13-inch sheet cakes, or sixty-four cupcakes.