For most recipes, one pound of icing sugar equals about 3 ½ to 4 cups. Yes, there’s a little wiggle room, because life—and sugar—is messy. If you’re scooping straight from the bag without sifting, aim for 3 ½ cups. If you sift it first (which makes it light and fluffy), you’ll get closer to 4 cups.
Why the difference? Icing sugar is a drama queen. It changes volume based on how you handle it. Think of it like packing a suitcase: if you cram things in, you fit less; if you gently lay them out, you need more space. Same goes for your powdered sugar.
Why Should You Care? (Besides the Obvious Panic)
Because icing sugar is not flour, and it’s not regular granulated sugar. It’s a delicate cloud of crushed crystals mixed with a little cornstarch. That cornstarch makes it fluffy, which is great for frosting but terrible for eyeballing measurements. Get it wrong, and your royal icing might turn into soup—or a brick.
Imagine this: you’re making a birthday cake for your best friend. You want the buttercream to be smooth, spreadable, and not a sugary landslide. Using the wrong cup-to-pound ratio is like inviting a bull into a china shop. Sure, it’s dramatic, but nobody wants the mess.
