What Is a Substitute for Caster Sugar?

What's the best caster sugar substitute?

Pulse granulated sugar in a food processor or high-powered blender for about 30 seconds. The result is sugar with a much finer texture, halfway between granulated and powdered sugar. This is functionally identical to commercial caster sugar.

Use the same amount as the recipe calls for (1 cup of homemade caster sugar replaces 1 cup of commercial caster sugar). The DIY version stores fine in a sealed container for weeks, though it can clump slightly if humidity is high.

Can you just use granulated sugar instead?

In most recipes, yes. Granulated sugar works as a 1-to-1 substitute for caster sugar, though it dissolves more slowly. For most baking applications (cookies, cakes, quick breads), the slower dissolving doesn't affect the final result.

For meringues and other recipes where the sugar needs to dissolve completely into beaten egg whites, granulated sugar can leave a grainy texture. For these recipes, processing the sugar first (or using actual caster sugar) makes a noticeable difference. Cocktails where sugar is shaken or stirred (Old Fashioned, Daiquiri) also benefit from finer sugar.

What about powdered sugar (confectioners' sugar)?

Powdered sugar is too fine and contains cornstarch, so it's not a direct substitute for caster sugar. Using powdered sugar in a recipe that calls for caster sugar would add about 3 percent cornstarch to the recipe, which can change the texture.

For recipes where the cornstarch doesn't matter much (basic cookies, simple cakes), powdered sugar can substitute in a pinch. Use 1 3/4 cups of powdered sugar for 1 cup of caster sugar, since powdered sugar weighs less per cup. For recipes that need precise texture (meringues, sponge cakes), the cornstarch matters and powdered sugar isn't a good substitute.

When does the caster sugar substitute matter most?

Meringues and pavlovas: caster sugar's quick-dissolving property is essential for smooth meringue texture. Granulated sugar leaves graininess that affects the mouthfeel. The DIY substitute (processed granulated sugar) is the closest match.

British and Australian recipes: many recipes from these regions assume caster sugar and won't work as well with American granulated sugar without processing it first. Light, airy sponge cakes also benefit from caster sugar because the fine texture incorporates better during creaming. For most American recipes (which assume granulated sugar), this conversion isn't necessary.