What Is Caster Sugar? Here’s What You Need to Know

Caster sugar is a common ingredient in British baking recipes, so if you’re an experienced baker (or just a superfan of The Great British Bake Off), you probably already know what it is. In the United States, however, caster sugar is much less common, so if you’ve never heard of it, don’t worry: we’re here to clue you in. Keep reading to learn what caster sugar is, how to cook and bake with it, and what the best substitutes for caster sugar are.

What Is Caster Sugar?

So, what is caster sugar? Caster sugar is finely ground granulated sugar. The granules of caster sugar are finer than those of granulated sugar, which allows them to dissolve more rapidly. For this reason, caster sugar can be preferable to granulated sugar for certain recipes, like cocktails, mousses, and whipped cream, where fast dissolution is helpful. Caster sugar is finer than granulated sugar, but coarser than powdered sugar, and each variety has its place.

In the United States., caster sugar isn’t always available at standard grocery stores. If it’s not at your local shops, you can purchase it from online retailers. Keep in mind that it’s typically called superfine sugar instead of caster sugar in America. If you find both white caster sugar and golden caster sugar, know that they are pretty much interchangeable. The main difference is that golden caster sugar is made with unrefined cane sugar and has a slightly more caramelly flavor, whereas white caster sugar is made with refined sugar and has a slightly purer, cleaner taste.

Caster Sugar vs. Granulated Sugar

Caster sugar is finer than granulated sugar, which means that it dissolves more easily. Although granulated sugar can certainly be used for baking, professional bakers often prefer working with caster sugar because it blends seamlessly into cake batters, meringues, and more. It depends on the recipe, but these two types of sugar are pretty interchangeable.

Caster Sugar vs. Confectioners’ Sugar

Confectioners’ sugar is much finer than caster sugar—it’s sugar that’s been ground so finely that it becomes a soft powder. It’s a useful ingredient, commonly used in glazes, icings, and as a festive, snowy dusting for any baked good. In order to prevent clumping, confectioners’ sugar is usually mixed with a bit of cornstarch, whereas caster sugar only contains sugar. Caster sugar and confectioners’ sugar are generally not interchangeable. 

How to Cook With Caster Sugar

You can cook with caster sugar the same way you’d cook with granulated sugar; just think of caster sugar as granulated sugar that dissolves more easily. Try whisking it into a peanut sauce for this Peanutty Soba Noodle Salad, or using it for a sugar rim for a batch of  Spicy Jalapeño-Mint Margaritas. To test its baking abilities, try replacing granulated sugar with caster sugar in these Pumpkin Cream Puffs, Pine Nut Drops, or Marbled Pound Cake—the options are endless. 

Caster Sugar Substitutes

If you can’t find caster sugar at the grocery store and don’t have any at home, give these suitable caster sugar substitutes a whirl instead.

Granulated Sugar

The most reliable and widely available substitute for caster sugar is granulated sugar, which can be swapped in a 1:1 ratio. If you think granulated sugar is too gritty for the recipe, you can blitz it briefly in a food processor so it will better mimic caster sugar.

Brown Sugar

Brown sugar can sometimes be used as a 1:1 substitute for caster sugar, but only on a case-by-case basis in particular recipes. Brown sugar adds moisture and a molasses flavor, which can be nice in rich, sweet foods like brownies and chocolate chip cookies, but not always.

Confectioners’ Sugar

Avoid confectioners’ sugar as a swap for caster sugar in baking recipes, but it can be a suitable 1:1 substitute in recipes like frosting, whipped cream, and fruit sauces. Just remember that confectioners’ sugar typically contains cornstarch, which affects foods’ texture.