Knowing how many cups in a pound of powdered sugar saves a store run

A 1 pound box of powdered sugar gives you about 3 3/4 cups, unsifted. That's the figure both Domino and Imperial Sugar's conversion chart print, and it's a quarter cup shy of what a lot of frosting recipes ask for.

So if you've ever wondered how many cups in a pound of powdered sugar before a bake sale, the honest answer is "slightly fewer than you need." The gap is small in volume but big in outcome, because it's usually discovered at 9 p.m. with a half-frosted cake on the counter.

How many cups in a pound of powdered sugar, by bag size

Manufacturers measure confectioners sugar unsifted, scooped into the cup and leveled. Domino lists 3 3/4 cups for a 1 lb box and 7 1/2 cups for a 2 lb bag, and Imperial prints the same two numbers. The gram column below uses the standard 453.6 g pound.

Rule of thumb: one 1 lb box of powdered sugar is 3 3/4 cups. If a recipe calls for 4 cups or more, buy the 2 lb bag.

Why 1 cup powdered sugar in grams isn't the same everywhere

Powdered sugar is mostly air. How you fill the cup decides how much sugar actually lands in it, and published weights disagree by a surprising amount.

The spoon-and-level number is 113 grams

The King Arthur ingredient weight chart puts 1 cup of unsifted confectioners' sugar at 4 ounces, or 113 grams. That's a light, spooned cup. For comparison, the same chart lists granulated sugar at 198 g per cup, so a cup of the powdered stuff weighs barely more than half as much.

The box math works out closer to 121 grams

Divide 454 g by the 3 3/4 cups printed on the box and you get roughly 121 g per cup. Plenty of recipe writers round that to 120 g. LorAnn's American buttercream, for example, lists 4 cups of powdered sugar as 480 g, which is exactly 120 g a cup.

Seven grams a cup sounds trivial. Over a 4 cup batch it's 28 g, close to a quarter cup of sugar, which is enough to change how stiff your frosting pipes.

Powdered sugar cups to grams for frosting and glaze

If a recipe gives grams, follow the grams. If it only gives cups, you have to guess which cup the author meant. Here's how the two common conventions compare, so you can match the recipe's own math.

A buttercream frosting recipe by weight

LorAnn's version is a good baseline: 226 g softened unsalted butter, 480 g powdered sugar, 2 tablespoons heavy cream, 1 teaspoon vanilla and 1/2 teaspoon salt. Weighing the butter is easy since it's two sticks, and our guide to how much a stick of butter weighs covers the 113 g math.

Powdered sugar glaze needs very little liquid

Most glaze recipes start with 1 cup of powdered sugar and 1 to 2 tablespoons of milk, then add liquid half a teaspoon at a time. Too thin? Whisk in more sugar a tablespoon at a time. That's the simplest icing from powdered sugar you can make, and it doesn't need butter at all.

What a box of confectioners sugar actually covers

Here's where the numbers turn into money and trips to the store. A 1 lb box holds 454 g. One batch of that 480 g buttercream needs 26 g more than the box contains, so a single box falls just short of a classic powdered sugar frosting.

A 2 lb bag, at 907 g, covers one full batch with 427 g left over for a glaze or a dusting. Doubling the recipe needs 960 g, though, so even the big bag runs 53 g short. Plan on two 2 lb bags if you're frosting for a crowd.

A 1 lb box holds 454 g of powdered sugar. A 4 cup buttercream at 120 g per cup needs 480 g. That 26 g gap is the reason for the late-night store run.

Checking a half-used bag is quick if you weigh it and convert with our grams to ounces converter. Just make sure the scale reads true first; our nickel calibration trick takes two minutes.

How to make powdered sugar when the bag runs out

Ran out anyway? Blend 1 cup of granulated sugar with 1 tablespoon of cornstarch for about 30 seconds, until it's white and fluffy. Love and Lemons notes the volume roughly doubles, so 2 cups of granulated sugar makes about 4 cups of homemade icing sugar.

Weight is the trick that keeps this honest. Volume doubles in the blender but the grams don't change, so 198 g of granulated sugar becomes about 198 g of powder plus the cornstarch. If your recipe lists grams, weigh the homemade powder and it'll behave like the boxed kind.

Quick answers about icing sugar and confectioners sugar

Is icing sugar the same as confectioners sugar?

Yes. Icing sugar, powdered sugar and confectioners sugar are names for the same finely ground sugar. Domino's 10X powdered sugar is pure cane sugar with a little cornstarch added to stop it caking.

Should you sift powdered sugar before measuring?

Only if the recipe says "sifted" before the measurement. Both the 113 g figure and the 3 3/4 cups per pound figure are for unsifted sugar, and sifting first puts fewer grams in every cup.

How many cups are in a 2 pound bag of powdered sugar?

About 7 1/2 cups, unsifted, according to both Domino and Imperial. That's 907 g, enough for one 480 g batch of buttercream with plenty left for a glaze.

Need to check how much powdered sugar is left in that bag before you head out? Download Scale for Grams and get an AI-powered weight estimate from a photo in seconds. Get the app here: iOS.