Powdered sugar — also called confectioners' sugar or icing sugar — is white granulated sugar that has been ground to an extremely fine powder and blended with a small amount of cornstarch (typically 3%) to prevent clumping. Its ultra-fine texture allows it to dissolve almost instantly, making it indispensable for smooth frostings, glazes, buttercream, and dusted finishes on pastries. It's also used in shortbread cookies and certain candy recipes where a smooth texture is essential.
What makes powdered sugar unique isn't just its sweetness — it's the texture it creates. When mixed with fat and liquid, it produces a smooth, stable, and pipeable frosting that holds its shape without grittiness. This is why swapping in granulated sugar for powdered sugar in a buttercream frosting is not a simple 1:1 substitute — the texture would be completely wrong. The fine particle size is the functional key, not just the sweetness.
If you find yourself without powdered sugar, your best option in most cases is to make it yourself — it takes only about a minute with the right equipment. Beyond that, there are a few commercial alternatives designed for specific dietary needs, including low-carb and sugar-free baking. Understanding what your recipe actually needs from the powdered sugar will help you pick the right path.
■Best Substitutes for Powdered Sugar
These substitutes are most relevant for frostings, glazes, dusting, and confection recipes. Ratios assume you're replacing 1 cup of powdered sugar.
| Substitute | Flavor / Texture Match | Swap Ratio |
|---|---|---|
| Homemade powdered sugar (blended white sugar) | Nearly identical; slightly coarser | Blend 1 cup white sugar + 1 tbsp cornstarch for ~1¾ cups powdered |
| Coconut sugar (finely blended) | Caramel flavor; light brown color | Blend to powder; use 1:1 by weight |
| Powdered erythritol | Very similar texture; zero calorie | 1:1 by volume (check brand label) |
| Powdered monk fruit sweetener | Clean sweetness; zero calorie | 1:1 by volume (check brand label) |
| Oat flour + sweetener | Mild flavor; slightly different texture | Not ideal for frosting; best for dusting |
| Powdered coconut milk | Works for dusting only; different flavor | Not a sweetener substitute; decorative use only |
| Superfine (caster) sugar | Dissolves faster than regular but still granular | Works in drinks/sauces; NOT suitable for frosting |
■How to Choose the Right Substitute
The most important question to ask is: what is the powdered sugar doing in this recipe? If it's being used to dust a finished pastry or cookie for presentation, your options are widest — even a light coating of fine cornstarch-based mixture or coconut sugar powder can work. If it's going into a frosting or buttercream, you need a true powder with extremely fine particle size and the ability to dissolve smoothly in fat and liquid.
For frosting and glazes, homemade powdered sugar is by far the best substitute. Use a high-powered blender or food processor to blitz 1 cup of white granulated sugar with 1 tablespoon of cornstarch for 45–60 seconds until you achieve a very fine, flour-like powder. Let it settle before opening the blender to avoid a sugar cloud. The cornstarch is important — it mimics the anti-caking agent in commercial powdered sugar and helps the frosting hold its structure.
For low-carb and keto baking, powdered erythritol is an excellent substitute that behaves very similarly to confectioners' sugar. Many brands sell it pre-powdered specifically for this use case. Powdered monk fruit blends (often combined with erythritol) are another good option. One caveat: erythritol can recrystallize in refrigerated frostings, sometimes producing a slightly gritty texture after chilling. Using a small amount of cream cheese or butter in the frosting can help minimize this effect.
■Frequently Asked Questions
Can I just blend regular sugar to replace powdered sugar? Yes, and it works quite well. Use a high-powered blender (not a food processor alone — a blender with a tamper is more effective) and blend 1 cup of white sugar with 1 tablespoon of cornstarch for about 60 seconds. The result will be finer than what you'd get from a food processor but slightly coarser than commercial powdered sugar. For most frostings and glazes, the difference is negligible.
Why does powdered sugar contain cornstarch? Cornstarch serves as an anti-caking agent — it absorbs moisture and prevents the fine sugar particles from clumping together. It also stabilizes frostings by absorbing excess liquid and giving the frosting body. When making homemade powdered sugar, including the cornstarch is important for texture, especially in buttercream.
Can I use caster (superfine) sugar instead of powdered sugar? For beverages and simple syrups, caster sugar is a decent swap since it dissolves more readily than regular granulated sugar. However, it is not suitable for frostings, glazes, or dusting — the particle size is still far too coarse to produce the smooth, silky texture that powdered sugar provides.
Is powdered erythritol a good keto substitute for powdered sugar? Yes, powdered erythritol is widely considered the best keto-friendly substitute for powdered sugar. It measures 1:1, dissolves well in frostings, and doesn't have the strong aftertaste of stevia. The main downside is a slight cooling sensation when eaten in large amounts, and potential recrystallization in refrigerated items.
Can I use powdered sugar in place of granulated sugar? Technically yes, but you'll need to use about 1¾ cups of powdered sugar for every 1 cup of granulated sugar (since powdered sugar is less dense). The extra cornstarch can slightly affect the texture of baked goods, making them a bit more tender. It's best to only do this swap when necessary.
See also: Food Substitutes Guide | White Sugar Substitutes | Cornstarch Substitutes