What Exactly Is Caster Sugar? Here's Everything You Need To Know

If you’re an avid baker—like many of us in the South are—then there’s a chance you’ve come across a recipe or two that calls for caster sugar. So what exactly is this unique ingredient, what makes it different from the usual granulated sugar, and what’s it used for? We’ve got your answers.

What Is Caster Sugar?

“In a nutshell, caster sugar (sometimes spelled castor sugar) is finely ground granulated sugar,” says Melissa Araujo, chef and owner of Alma Café in New Orleans. “It’s got some grit to it though, so it’s not as fine as confectioners’ sugar. I’d say it falls somewhere in between granulated and confectioners.” Caster sugar can be used in almost any way granulated sugar is used, but its texture proves to be better in certain circumstances. It’s used most often in baking and when a recipe calls for a sugar that needs to dissolve quickly when mixed in with other ingredients (like egg whites or butter). 

Most frequently you’ll find caster sugar used in cookies, cakes, and meringues in the UK and Australia. While it’s not as common here in the American South, you can likely find it at the supermarket in the baking aisle labeled as “superfine sugar.” It’s also possible you’ve seen this type of sugar in a metal shaker (called a caster) that’s meant to be shaken on pancakes or fruits.

Caster sugar is available in two different varieties: a regular (white) version and a golden variety. Golden caster sugar is unrefined and processed in a way that allows it to maintain some of its natural molasses—kind of like brown sugar. Compared to white caster sugar, the flavor of golden caster sugar is a bit warmer and more caramel-like.

How Is Caster Sugar Different From Other Sugars?

“The only difference between caster sugar and other white sugars like granulated sugar and powdered sugar is the texture,” says Araujo. Caster sugar’s crystals are more finely ground, but not completely powdery, which allows for them to dissolve faster than granulated sugar in creamed mixtures and whipped substances. 

“Since caster sugar dissolves and incorporates quicker than granulated sugar, it makes it perfect for light and airy desserts,” says Araujo. “I love using it for meringues and soufflés. It's also often used to sweeten beverages, such as tea because it doesn't need heat to dissolve. It makes for a perfect summertime sweet tea.”

Caster Sugar Vs. Granulated Sugar

Granulated sugar is more coarse and has a larger grain than caster sugar. While they are typically interchangeably, granulated sugar has a knack for not incorporating into batters as quickly as caster sugar does. Cakes and other desserts that are baked with granulated sugar instead of caster sugar may have a speckled appearance that’s thanks to the undissolved granules.

Caster Sugar Vs. Powdered Sugar

Powdered sugar is finer than caster sugar, and the two are usually unable to be used in place of each other. Powdered sugar (often referred to as confectioners’ sugar) is a finely ground granulated sugar that’s mixed with a small amount of cornstarch in order to eliminate clumping. It's commonly used to make frosting and icing or often dusted over desserts. 

What Can I Use As A Caster Sugar Substitute?

If you’re in a pinch and a recipe calls for caster sugar, but you don’t have any on hand, granulated sugar will usually work as an easy alternative. Some tips to keep in mind: if it’s a recipe that involves making a meringue, use a lower speed to mix the sugar and egg whites so that the sugar can dissolve completely. If you’re creaming butter and sugar together, start with slightly colder than room temperature butter and mix it longer than usual so the sugar has the chance to really incorporate in the same way that caster sugar would.

How To Make Caster Sugar

Make your own caster sugar easily at home with granulated sugar and a food processor. For every one cup of caster sugar that your recipe calls for,  you’ll need one cup, plus two teaspoons of granulated sugar. In a food processor, grind the granulated sugar until it’s fine in texture, but it is not fine enough to form a powder that starts to clump together—it should take just a few seconds. “A coffee grinder or spice grinder would work too,” says Araujo. “For best results, run your homemade caster sugar through a fine strainer for optimal fluffiness.”