What Is Caster Sugar?

A Guide to Buying, Using, and Storing Caster Sugar

what is caster sugar

The Spruce Eats / Lindsay Kreighbaum

Caster sugar is the term for very fine granulated sugar in the United Kingdom. British bakers and cooks value it for making meringues, custards, candies, mousses, and a number of baked goods. In the United States, caster sugar is usually sold under the name "superfine sugar." It is also sometimes referred to as baking sugar or casting sugar, and can be spelled as "castor." The term "caster" comes from the fact that the sugar was placed in a shaker, called a caster, and used to sprinkle on fresh fruit.

Fast Facts

  • Also Known As: Superfine sugar
  • Popular In: The U.K.
  • Used In: Desserts and beverages

What Is Caster Sugar?

Although caster sugar is finer than granulated, it retains some of the rough texture of sugar, unlike confectioners' sugar, which is more like a powder. Caster sugar's consistency falls in the middle between granulated and powdered sugars. It melts faster and incorporates into sauces, puddings, and bases more quickly than regular granulated sugar. If a recipe calls for caster sugar, regular sugar can be substituted, but the result may be grainy. Because caster sugar crystals are so fine, they dissolve quickly, making the sugar particularly suitable for sweetening cold drinks or cocktails.


Caster sugar is offered in both regular (white) and golden varieties. The golden is made from unrefined sugar cane or beets and during processing maintains some of the molasses, which gives the sugar a light brown color and slight caramel, buttery flavor. Although readily available in the U.K., golden caster sugar is more difficult to find than white caster sugar in the U.S.

Caster Sugar Uses

Because caster sugar is lighter in texture than granulated sugar, it is perfect for making meringues, soufflés, and mousses, and for sweetening whipped cream; it incorporates more easily and dissolves faster in egg whites and creamed mixtures. It also adds volume to cookies and cakes, and airiness to recipes such as Scottish shortbread. Caster sugar is the best sugar to use for sorbets and is delicious sprinkled over fresh fruit but is not recommended in frosting, icing, or buttercream. It's also the ideal sugar to incorporate into cold drinks since it dissolves quickly and doesn't create any syrupy layers.

How to Bake With Caster Sugar

Caster sugar is incorporated into recipes in the same manner as granulated sugar. It is simply measured and mixed with ingredients.

What Does It Taste Like?

Since caster sugar is granulated sugar that has been ground more finely, it has the same taste as regular white sugar.

Caster Sugar Recipes

This sugar is often used in British recipes but can be substituted for granulated sugar in American recipes where the finer texture would be welcome.

Where to Buy Caster Sugar

While caster sugar is readily available in the U.K., it may be difficult to find in the U.S. Some companies, such as Domino, market it under the name "superfine sugar," which may be easier to find in major supermarkets in the baking aisle. Otherwise, this sugar is easily found online and may be available at specialty baking supply stores and European markets. Take note that caster sugar also costs quite a bit more than granulated sugar.

If you have difficulty finding it or do not want to pay the high price, it is simple to make your own caster sugar using regular granulated sugar and a food processor. Keep in mind that the granules may not be of uniform size, but the mixture will still work in recipes. Alternatively, recipes that call for caster sugar can be altered slightly to accommodate the use of granulated sugar.


Caster sugar should be kept the same way that other sugars are stored. Keep in a cool, dry place away from moisture or heat.