How much sugar is in caster sugar?

January 9, 2026 •

2 min read

Caster sugar is 100% sugar, specifically sucrose, similar to granulated sugar. It differs in crystal size, not chemical composition, which affects its behavior in recipes. This makes it ideal for specific textures in baking.

Quick Summary

Caster sugar is entirely sucrose. Its defining feature is a finer crystal size, which dissolves quickly in baked goods and cocktails. This textural difference affects use in recipes, not its chemical makeup as a pure carbohydrate.

Key Points

100% Sucrose: Caster sugar is pure sucrose, like granulated sugar.
Fine Crystals: It has a finer crystal size, enabling faster dissolving.
No Additives: It lacks cornstarch or other anti-caking agents.
Same Nutrients: Nutritionally, it is the same as granulated sugar.
Ideal Texture: It is suitable for light bakes and cold liquids.
Make Your Own: You can make it by processing granulated sugar.

Caster sugar: All about the crystals

Caster sugar is highly refined white sugar, derived from sugar cane or sugar beets. During manufacturing, the juice is purified, evaporated, and crystallized. For caster sugar, crystals are ground finer than granulated sugar. This fine texture is the sole distinction, as both are pure sucrose.

The chemical breakdown

Caster sugar is a carbohydrate called sucrose, with the formula C${12}$H${22}$O$_{11}$. This disaccharide consists of glucose and fructose. Being refined, it contains virtually no other nutrients or fiber. Unlike powdered sugar, it lacks anti-caking agents, making it 100% pure sugar.

Why does crystal size matter?

The smaller crystals of caster sugar offer advantages for culinary applications:

Faster Dissolution: Dissolves rapidly in liquids, ideal for cocktails and whipping ingredients.
Smoother Texture: Creates even sugar distribution in batters, leading to a finer crumb and smoother finish.
Better Aeration: Helps incorporate air when creamed with butter, resulting in a lighter product.

Nutritional comparison: Caster sugar vs. granulated sugar

Nutritionally, differences between caster and granulated sugar are negligible. A standard teaspoon contains the same calories and carbohydrates. The choice depends on the desired texture.


Feature	Caster Sugar	Granulated Sugar
Crystal Size	Very fine, smaller than granulated	Standard, larger crystals
Primary Composition	Sucrose (approx. 100%)	Sucrose (approx. 100%)
Dissolving Speed	Dissolves quickly	Dissolves more slowly
Best For...	Meringues, soufflés, cocktails, light sponge cakes	All-purpose baking, general cooking
Nutritional Value	4g sugar, 16 kcal per teaspoon	4g sugar, 16 kcal per teaspoon

Can you substitute caster sugar with granulated?

In most recipes, granulated sugar can replace caster sugar at a 1:1 ratio. However, for delicate bakes, substitution might result in a grainy texture. Caster sugar can be made by pulsing granulated sugar in a food processor.

The takeaway

"How much sugar is in caster sugar" has a simple answer: it's all sugar. The name refers to the particle size, not a different chemical makeup. This understanding allows bakers to make informed decisions based on texture.

For more on sugar types, consult resources like the British Heart Foundation's guide.

Conclusion

Caster sugar is finely granulated sucrose, chemically identical to table sugar. The fine crystals are the only distinguishing feature, offering quick dissolving properties and an ability to create smoother, more uniform textures. Its nutritional profile is consistent with other forms of refined sugar. The choice is textural preference.

Frequently Asked Questions

No, both are pure sucrose and have the same nutritional profile. The difference is the crystal size.

Put granulated sugar in a food processor or blender and pulse for 1-2 minutes until it is fine. Avoid over-processing to prevent it from turning into powdered sugar.

Yes, you can substitute it in most recipes. However, for delicate recipes, it might result in a grainier texture.

Caster sugar is finely granulated sucrose without additives, while powdered sugar is ground into a very fine powder and usually contains an anti-caking agent, like cornstarch.

Recipes call for it when the final texture is important. The fine crystals dissolve quickly, which is ideal for smooth textures in mousses, meringues, or cakes.

Yes, its finer crystal size allows it to dissolve much faster in cold liquids.

Golden caster sugar has molasses, giving it a light color and subtle caramel flavor. It is less refined than white caster sugar but is still mostly sucrose.