Cups of Powdered Sugar to Grams Conversion
1 cup sifted powdered sugar = 120g
One cup of sifted powdered sugar weighs 120 grams. Unsifted powdered sugar weighs 150 grams per cup. That's a 25% difference.
Powdered sugar clumps. The fine grind attracts moisture from the air, forming hard lumps that throw off volume measurements. Professional bakers sift it first or weigh it. A recipe that calls for 2 cups of powdered sugar needs 240g if sifted, 300g if not.
Most recipes assume sifted powdered sugar unless they specifically say "packed" or "unsifted." When in doubt, sift. The extra minute prevents dense frosting and grainy glazes.
How to Convert
For sifted powdered sugar: multiply cups by 120 to get grams. For unsifted: multiply by 150.
Example calculation: Your recipe needs 1.5 cups sifted powdered sugar. Multiply 1.5 x 120 = 180 grams. Place a bowl on your scale, tare to zero, add powdered sugar until it reads 180g.
To convert grams to cups, divide by 120 (sifted) or 150 (unsifted). A recipe calling for 360g powdered sugar needs 360 / 120 = 3 cups if measuring sifted.
Always check if the recipe specifies sifted or unsifted. The terms "confectioners' sugar" and "icing sugar" mean the same thing as powdered sugar.
Common Mistakes
Measuring powdered sugar straight from the bag without sifting adds 30 grams per cup. Those lumps create pockets of concentrated sweetness in frosting. Not tapping or settling the measuring cup. Powdered sugar is so light it leaves air gaps. Tap the cup on the counter 2-3 times to settle it before leveling. Packing powdered sugar like brown sugar. Only pack it if the recipe specifically says "firmly packed powdered sugar," which is rare. Most recipes want it loose and airy. Using the wrong conversion ratio for your specific brand. Generic store brands often have coarser grinds that weigh 125-130g per sifted cup instead of 120g.
Pro Tips
Store powdered sugar with a few marshmallows in the container. They absorb moisture and prevent clumping. Replace the marshmallows every 2-3 months.
Sift directly onto parchment paper, then use the paper as a funnel to pour into your measuring cup or mixing bowl. No mess, no waste.
For ultra-smooth frosting, process store-bought powdered sugar in a food processor for 30 seconds. This breaks down any remaining lumps and adds air, making it closer to 115g per cup.
Make your own: blend 1 cup granulated sugar with 1 tablespoon cornstarch for 60 seconds. Fresh powdered sugar dissolves better than old stock.
Ingredient-Specific Notes
Sifted powdered sugar
120g per cup. Sift through a fine-mesh strainer or flour sifter before measuring. This is the standard assumption in most American recipes. The sifting process aerates the sugar and removes lumps, creating consistent texture in frostings and glazes.
Unsifted powdered sugar
150g per cup, sometimes up to 160g if very lumpy. Straight from the bag without sifting. Some recipes specifically call for unsifted when they want a denser result, like certain fudge frostings.
10X powdered sugar
Same as regular powdered sugar at 120g per cup sifted. The "10X" refers to how finely it's ground (10 times finer than granulated). Most US powdered sugar is 10X. Some specialty brands offer 6X or 4X, which are coarser and weigh 130-140g per cup.
Organic powdered sugar
125g per cup sifted. Often made with tapioca starch instead of cornstarch, which changes the density slightly. The grind is usually less fine than conventional powdered sugar. Check your specific brand.
Homemade powdered sugar
115g per cup when freshly made. Blending granulated sugar at home creates a fluffier product with more air incorporation. Settles to 120g per cup after sitting for 24 hours.
Frequently Asked Questions
Why does my powdered sugar have lumps?
Moisture. Powdered sugar contains 3% cornstarch to prevent caking, but humidity still causes clumping. Each lump can contain 5-10 times more sugar than the surrounding powder. Sift before measuring or your frosting will have sweet spots and grainy patches. Store in an airtight container with 2-3 marshmallows to absorb moisture. Replace marshmallows every 60 days.
Is confectioners' sugar the same as powdered sugar?
Yes. Also called icing sugar, 10X sugar, or superfine sugar (though superfine technically means something else). All refer to finely ground sugar mixed with 3% cornstarch. One cup sifted = 120g. The cornstarch prevents clumping and adds stability to whipped cream and meringues. Some European brands use wheat starch instead, same weight per cup.
How much powdered sugar equals 1 cup of granulated sugar?
Use 1.75 cups sifted powdered sugar to replace 1 cup granulated sugar (200g) in recipes. Powdered sugar weighs less per cup (120g vs 200g) and contains cornstarch. The substitution works for frostings and no-bake recipes. Don't substitute in cakes or cookies, the cornstarch affects texture and the fine grind changes how the sugar interacts with butter and eggs.
Should I measure powdered sugar before or after sifting?
Depends on the recipe wording. "1 cup sifted powdered sugar" means sift first, then measure (120g). "1 cup powdered sugar, sifted" means measure first, then sift (150g). Most recipes mean sift-then-measure. When recipes don't specify, assume sifted (120g per cup). The 30g difference per cup matters in buttercream ratios and glaze consistency.
Can I use granulated sugar instead of powdered sugar?
Not directly. Powdered sugar dissolves instantly, granulated sugar needs heat or lots of mixing. For frosting, blend granulated sugar in a blender for 60-90 seconds with 1 tablespoon cornstarch per cup. For dusting, process granulated sugar alone for 2 minutes. The homemade version weighs 115g per cup fresh, 120g after settling. Won't be as fine as commercial 10X grade but works for most purposes.