Sugars & Sweeteners
sugarprecisionsweetener

Caster Sugar

Superfine granulated white sugar that dissolves rapidly, ideal for meringues, soufflés, and light sponge cakes.

Caster Sugar — Sugars & Sweeteners kitchen reference
Quick conversion

1 Cup Caster Sugar = 225g (8.0 oz) • 1 Tbsp = 14g

Caster sugar (often spelled castor sugar) is white granulated sugar that has been ground to a crystal size that is midway between standard table sugar and powdered sugar. Because the crystals are extremely small and uniform, caster sugar dissolves much faster and more evenly than regular granulated sugar, without the risk of caramelizing unevenly or leaving gritty spots. This rapid-dissolving property makes it highly prized by pastry chefs for delicate preparations such as meringues, soufflés, syrups, and light, airy sponge cakes. When whipping egg whites for meringues, caster sugar dissolves quickly, preventing sugar syrup from weeping out of the baked foam.

In the creaming process, the superfine crystals of caster sugar create smaller, more densely distributed air pockets in butter, resulting in a cake with a tighter, more uniform crumb structure. It is the standard sugar used in British and Australian baking, where precision and delicate cake textures are highly valued.

Common mistake

Using regular granulated sugar in cold cocktails or delicate egg foams. The large crystals do not dissolve fully, settling as a gritty residue at the bottom of the bowl or glass.

US vs UK / Metric

In the United States, this is sold as Superfine Sugar or Quick-Dissolve Sugar. In the UK and Australia, it is universally labeled as Caster Sugar.

When to use it

Best for meringues, soufflés, sponge cakes, curds, custards, and sweetening cold drinks or cocktails.

Substitution

Replace 1 cup caster sugar with 1 cup granulated sugar pulsed in a food processor or clean coffee grinder for 30 seconds.

Storage tip

Store in an airtight container in a dry pantry indefinitely to prevent clumping.

Try the caster sugar converter