What Is Caster Sugar?

Perhaps you've come across caster sugar in a recipe. Here are some answers to the questions you might have been wondering, including where to buy caster sugar, what the best substitute is and how to make it yourself.

June 25, 2021



Photo by: antonios mitsopoulos/Getty Images

antonios mitsopoulos/Getty Images

By Jessie Sheehan for Food Network Kitchen

Jessie Sheehan is a baker and cookbook author.

If you bake, chances are you have come across a recipe calling for caster sugar. Perhaps the recipe was English or Australian. Below you will find answers to the following pressing questions: What is caster sugar? Where can I buy caster sugar? What can I substitute for caster sugar and – most importantly – how can I make my own caster sugar?

Homemade meringues on ceramic plate and linen fabric


Homemade meringues on ceramic plate and linen fabric

Photo by: AnastasiaNurullina/Getty Images

AnastasiaNurullina/Getty Images

What Is Caster Sugar Made of?

In a nutshell, caster sugar (sometimes spelled castor sugar) is finely ground granulated sugar. It is not as fine as confectioners’ sugar, as it does have a little grit to it, and is not powder-y. So, in terms of texture, it falls somewhere between granulated and confectioners’. You will often see it in English and Australian baking recipes for cookies, cakes and shortbread, as it is widely available in the grocery stores of both countries, and is basically the go-to baking sugar, as it were. Mary Berry, the queen of British baking, writes in Mary Berry Baking Bible that caster sugar’s fine grains are ideal for “whisked sponges, cream mixtures, and meringue.” So, there’s that, too.

What is Caster Sugar in the US?

What is caster sugar in the US called, you ask? Well, it is called superfine sugar and guess what? You can likely find it at your local grocery store. Unfortunately, it is not typically sold in a particularly large container, so it is not the kind of thing that you will always have on hand (unless you buy it in bulk), but it shouldn’t be hard to find in the baking aisle when you do need it.

Add caster sugar to dough and mix to form soft dough. Making Boston Banoffee Pie.

1073867584/Getty Images

Add caster sugar to dough and mix to form soft dough. Making Boston Banoffee Pie.

Photo by: vinicef


Caster Sugar vs. Granulated Sugar

Caster Sugar is granulated sugar’s “finer” cousin and because of this, it dissolves more easily than granulated sugar, and weighs a bit more, as well, when measured via volume (i.e.: a cup of caster sugar weighs about 225 g and a cup of granulated weighs in at around 200 g). Whereas Mary Berry prefers caster when creaming butter and sugar for cakes, as mentioned above, because of its solubility, she prefers granulated when melting and when rubbing butter into sugar and flour with your fingertips.

Caster Sugar vs. Confectioners’ Sugar

Caster sugar has less in common with confectioners’ sugar than it does with granulated, as confectioners’ sugar is quite literally ground so fine that it is reduced to a powder. And just as you would turn to confectioners’ sugar, as opposed to granulated, when whipping up an American buttercream frosting, for instance; you would also choose confectioners’ over caster. Although fine, the caster grains are not quite fine enough for that application.

Scottish Shortbread Fingers arranged on an English napkin.

593392690/Getty Images

Scottish Shortbread Fingers arranged on an English napkin.

Photo by: Nick Bubb www.imagecaptured.co.uk

Nick Bubb www.imagecaptured.co.uk

What Kind of Recipes Call for Caster Sugar?

If it is a baking recipe from the UK or Australia, then it is likely that caster sugar will be the sugar of choice in everything from cookies to cakes to meringues. Recipes in the US tend to call for superfine sugar (the American equivalent of caster) much less frequently, like for cocktails, some ice creams and meringues, to name a few.

Where to Buy Caster Sugar

If you do not want to substitute superfine sugar for caster sugar, you can purchase caster sugar online at a variety of different sites. And if there is a specialized baking supply store near you, they will most likely carry it, as well.

Caster Sugar Substitute

Superfine sugar, widely available in the US, is the best substitute for caster sugar.

You might also be wondering: “Can you just substitute granulated sugar for caster sugar?” You can, but we wouldn’t recommend it. If the recipe lists the weight of the caster sugar, as opposed to the volume/cup measurement, then you will likely be okay substituting weight for weight; particularly if the recipe is English or Australian and is for cookies or a simple cake. But if the amount of caster sugar is only listed in volume, you will have trouble. As stated above, a cup of caster sugar weighs more than a cup of granulated. Thus, if you substitute a cup of granulated for a cup of caster, you will be substituting with less sugar than what the recipe requires. Moreover, for those recipes that call for caster sugar because of its aforementioned solubility, granulated is obviously a poor substitute, as the finished product may be gritty due to undissolved grains of sugar.

How to Make Caster Sugar

Making your own caster sugar is easy-peasy, as long as you have a food processer. Essentially you pour granulated sugar into the work bowl of your food processer and process it until finely ground, about 1 to 2 minutes depending on the quantity. It is a good idea to put a bit more sugar than that which your recipe calls for in the bowl, as you may lose some of it to an unsalvageable finely ground powder.

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