Unsifted is the headline convention
King Arthur Baking lists unsifted confectioners' sugar at 113 g per US cup. PantryGauge calculates 100 ÷ 113 = 0.88 cup and labels the result unsifted, spooned, and levelled.
If a recipe says sift the sugar before measuring, sift first and then measure. Sifted sugar occupies more volume, so it is not honest to reuse the unsifted number without a caveat.
Powdered, icing, and confectioners' sugar
These names often refer to similar fine sugar products, but brands and starch content can vary. Use the product and method named in the recipe, and weigh the sugar when a frosting formula needs a repeatable ratio.
Do not pack powdered sugar unless the recipe explicitly asks for it. Pressing clumps into the cup creates a different density from spooning and levelling.
Why published answers disagree
Current conversion pages report values from about three-quarters of a cup to nearly nine-tenths for 100 g. The disagreement reflects sifted versus unsifted states, different cup references, and different filling methods—not a reason to invent one exact universal fraction.
Questions readers ask
How many cups is 100 g of powdered sugar?
Using King Arthur Baking's 113 g-per-US-cup unsifted reference, 100 g is about 0.88 cup.
Is 100 g powdered sugar three-quarters of a cup?
It can be close when a chart uses a heavier grams-per-cup convention, but PantryGauge's unsifted reference gives about 0.88 cup. The sifting state must be named.
Is icing sugar the same as powdered sugar?
The terms are often used for similar fine sugar, but brand formulation and starch can vary. Follow the package or recipe wording.
Should I sift before or after measuring?
Follow the recipe. ‘Sifted and measured’ and ‘measured and sifted’ are different instructions, so do not silently swap them.
Sources and method
Numerical answers are tied to the stated ingredient, state, cup convention, and source. Derived values are calculated from the cited reference and rounded for kitchen use.