Baking
Powdered Sugar Conversion
Powdered Sugar weighs 120g per US cup.
| Amount | Grams | Ounces |
|---|---|---|
| 1 cup | 120.0 g | 4.23 oz |
| 1/2 cup | 60.0 g | 2.12 oz |
| 1/4 cup | 30.0 g | 1.06 oz |
| 1 tbsp | 7.5 g | 0.26 oz |
| 1 tsp | 2.5 g | 0.09 oz |
| 100 g | 100.0 g | 3.53 oz |
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Powdered sugar weighs just 120 grams per cup — five-eighths of granulated sugar's 200g, despite being the same base ingredient — because it's been pulverized into an extremely fine powder and blended with about 3% cornstarch to prevent caking, and that fine, aerated structure traps far more empty space per cup than coarse granulated crystals do.
That cornstarch content isn't just an anti-caking afterthought — it also means powdered sugar isn't a pure sweetener the way granulated sugar is, which matters in a recipe sensitive to starch content, though for icings, glazes, and dusting (its overwhelming majority use case) the small cornstarch percentage is essentially unnoticeable.
Powdered sugar dissolves almost instantly into liquid without any graininess, which is exactly why it's the standard choice for icings and glazes rather than granulated sugar — granulated sugar's larger crystals need heat or prolonged mixing to dissolve fully, while powdered sugar's fine particles disperse smoothly into a cold liquid on contact.
Powdered sugar's featherlight 120g-per-cup weight — nearly 40% lighter than granulated sugar's 200g/cup — comes from how finely it's ground plus the small amount of cornstarch (roughly 3%) manufacturers add to prevent clumping; that combination of fine particle size and added starch traps considerably more air per cup than granulated sugar's uniform crystals do.
That added cornstarch is also why powdered sugar isn't a clean substitute for granulated sugar in recipes relying on sugar's crystalline structure (meringues, some cookie textures) — the starch changes both the dissolving behavior and, in larger quantities, the finished texture.
It's sometimes labeled confectioners' sugar or icing sugar, all referring to the same finely milled product.
Sifting it before use breaks up clumps that form during storage, giving a smoother finished glaze or frosting.
A basic glaze is often nothing more than powdered sugar whisked with a small amount of milk or water until pourable, with the exact ratio adjusted by eye until the consistency drips slowly off a spoon rather than running thin.
Frequently asked questions
Can I make powdered sugar from granulated sugar at home?
Yes — blending granulated sugar in a high-speed blender or food processor until fine works in a pinch, though homemade versions typically stay slightly grainier than commercial powdered sugar and lack the anti-caking cornstarch, so they can clump faster in storage.
Why does powdered sugar have cornstarch in it?
The cornstarch (about 3% by weight) keeps the extremely fine sugar particles from caking together into a solid mass — without it, powdered sugar's fine texture would clump almost as readily as brown sugar does without proper sealing.
Can I substitute powdered sugar for granulated sugar 1:1 in baking?
Not reliably — powdered sugar's added cornstarch and much finer texture changes both the structure and the moisture balance of a batter, so recipes calling for granulated sugar shouldn't be swapped straight across without testing.
Is confectioners' sugar the same as powdered sugar?
Yes — "confectioners' sugar," "powdered sugar," and "icing sugar" (the common UK term) all refer to the same finely ground, cornstarch-blended product, just under different regional names.
Does sifting powdered sugar before using it matter?
Often yes — despite being fine to begin with, powdered sugar can develop small clumps in storage, and sifting it before adding to a glaze or dusting a cake helps avoid visible lumps in the finished result.