Powdered Sugar: Sifting, Weight & Baking Guide

Finely ground sugar with a little starch — the base of icings, glazes, and dustings.

1 cup = 120g

Powdered sugar

Measured

spooned and leveled

What is powdered sugar?

Powdered sugar is granulated sugar ground to a fine powder, usually with a few percent cornstarch mixed in to stop it caking. Its fine grind dissolves instantly, which is why it’s the base for icings, glazes, and dustings rather than for structure. A cup weighs about 120 grams unsifted.

Because it’s so fine, it compacts and clumps easily, and sifting can change a cup’s weight by around 20 grams. When a recipe’s texture depends on it — smooth royal icing, a stable buttercream — weigh it: 1 US cup unsifted is about 120g.

Measurement profile

Grams per cup: 120g
Cup standard: US cup / 240 ml
Ingredient state: unsifted
Confidence: Medium

Data last verified: August 4, 2026

Source observations

USDA FoodData Central — Sugars, powdered (FDC 169656)120 g/1 source cup, unsifted (exact volume unknown) · unsifted, spooned
King Arthur Baking — Ingredient Weight Chart113 g/1 source cup, unsifted (exact volume unknown) · unsifted, spooned and leveled

Why measurements vary

Sifting

Sifting breaks clumps and adds air, making a sifted cup lighter than an unsifted cup.

Humidity and packing

Moisture creates dense clumps, while pressing the powder removes air and raises the cup weight.

How to measure powdered sugar

spooned and leveled

Powdered sugar is light and airy, so spoon it into the cup and level it rather than packing it down.
Sifting powdered sugar before measuring can reduce clumps and slightly lower the weight per cup.
Humidity easily makes powdered sugar clump, which can add extra weight if it is not broken up before measuring.

Types & varieties

Confectioners' sugar (unsifted)

120g per cup

Standard 10X grind with a little cornstarch to prevent caking.

Sifted powdered sugar

Aerated by sifting, so a cup weighs less.

Icing sugar

The same product under its British name.

Common powdered sugar measurements

These limited reference values are derived from the canonical cup weight. Use the converter for any other amount.

Cups	Grams
¼ cup	30g
⅓ cup	40g
½ cup	60g
1 cup	120g

Common substitutes

Granulated sugar (blended)

Blend 1 cup granulated sugar with 1 tsp cornstarch until powdery.

Superfine sugar

Dissolves easily, but won't give the same smooth, starchy body in icings.

Related measurement resources

Convert powdered sugar grams to cups

Convert cups of powdered sugar to grams

Browse related ingredient guides

How ingredient measurements are verified

Frequently asked questions

How many grams are in 1 cup of powdered sugar?

1 US cup of unsifted powdered sugar weighs about 120 grams. Sifting adds air, dropping it closer to 100 grams, so it matters whether a recipe says "sifted."

Does it matter if powdered sugar is sifted or not?

Yes. Sifted powdered sugar is lighter and lump-free, so "1 cup sifted" and "1 cup, then sifted" give different weights. Weighing avoids the ambiguity.

Can I make powdered sugar from granulated sugar?

Yes. Blend 1 cup of granulated sugar with about 1 teaspoon of cornstarch in a high-speed blender until it's fine and powdery.

Why does powdered sugar contain cornstarch?

A small amount of cornstarch (about 3%) keeps the fine sugar from clumping and helps thicken icings and glazes.