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Sugar types: what granulated, caster, brown and icing each do differently

By BakePen Editorial · Last updated 6 Sep 2026 · 6 min read

‘Sugar’ in a recipe is a family name, not an ingredient. Granulated, caster, brown and icing sugars are all sucrose at heart, but they differ in crystal size, moisture and acidity, and those differences change how a mixture creams, how a crumb sets, how a surface crusts and how long a bake stays soft. Swapping them casually is the quiet cause of many ‘the recipe didn't work’ afternoons.

This article gives each sugar its own honest description — what it is, what it does, when it can stand in for another, and when the substitution changes the bake enough that you should know you are making a different recipe.

Crystal size is a working property

Caster sugar's fine crystals dissolve quickly and cut into butter efficiently during creaming, trapping more, smaller air bubbles than coarse granulated sugar can. That is why sponges specify caster: the same weight of granulated gives a slightly coarser, sometimes speckled crumb, because undissolved crystals melt late and leave their ghosts. In a syrup, a meringue or a biscuit where spread matters more than aeration, the difference shrinks — granulated is fine, and cheaper.

Demerara and other coarse sugars barely dissolve in a bake at all, which is precisely their use: crunch on top of muffins and crumbles, sparkle on biscuits. Crystal size is a tool; each sugar is a different setting of it.

Brown sugar is a flavour and moisture decision

Brown sugar is sucrose with molasses — either retained from refining or added back — and the molasses brings moisture, a gentle acidity and a toffee depth. That moisture is why brown-sugar biscuits stay chewy: the sugar is hygroscopic, holding water in the crumb. Its acidity also reacts with baking soda, contributing lift, which is why so many biscuit recipes pair the two and why swapping brown for white in those recipes changes the rise as well as the taste.

‘Packed’ in a brown-sugar measurement is structural, not decorative: packed, a cup is 220 g; loose, the same cup might be 165 g. Recipes mean packed. It is the one sugar whose measuring technique is part of the ingredient, and the reason weighing brown sugar — 220 g per cup, packed basis — settles so many arguments.

Muscovado and other dark, unrefined sugars deserve a mention at the family's deep end: they carry more molasses than light brown sugar, a damper texture, and a flavour that can dominate a delicate bake while glorifying a spiced one. They measure like brown sugar — packed, 220 g to the cup as a working figure — and they keep their moisture best in an airtight jar, hardening dramatically when abandoned to the air. In fruit cakes, gingerbreads and anything built on spice, muscovado is not a substitution but an upgrade with intent; in a pale sponge it is a plot twist. Knowing which sugar is a seasoning and which is a sweetener is the last refinement this family asks of a baker.

Icing sugar and the fine end

Icing (confectioners') sugar is sucrose ground to powder with a little cornflour to keep it flowing — about 120 g to a loose cup, and as little as 100 g sifted. Its fineness makes frostings smooth and dustings snowy, and its cornflour content slightly thickens what it joins. In cakes it produces a very tender, fine crumb and is the backbone of some traditional sponges; in meringues it folds in where granulated would weep.

The traps are two: substituting it by volume without converting the weight (a cup of icing for a cup of granulated under-sugars by 80 g), and expecting it to cream — powder has no crystals to cut air with, so a sponge built on it needs its lift from the eggs.

Swapping sugars without surprises

Granulated and caster swap weight for weight in almost anything, with texture differences only in fine sponges and meringues — caster is the safer default for cakes, granulated for syrups and sturdy biscuits. White for brown, weight for weight, keeps sweetness but loses moisture and chew; add nothing else and accept a crisper bake. Brown for white deepens flavour and softness and darkens colour — welcome in spice cakes and biscuits, a lie in a white Victoria sponge.

Liquid sweeteners — honey, golden syrup, maple — are a different negotiation involving water content, and they get their own article; the short version is that they are never a dry-for-dry swap. Within the dry sugars, though, weight is the great stabiliser: convert by grams, honour the moisture differences, and swaps become choices rather than accidents.

The dry sugars compared

The chewy biscuit that went crisp

A biscuit recipe built on 200 g of packed brown sugar and soda comes out chewy and deep-flavoured. The next week the cupboard offers only white granulated, swapped cup for cup — which is also 40 g less sugar by weight, no molasses moisture, and no acid for the soda to work against. The biscuits bake crisp, pale and flatter, and spread differently. Nothing failed; a different recipe was baked. Weighed and understood, the swap could have been a deliberate variation instead of a surprise.

Common mistakes

Measuring brown sugar loose. An unpacked cup can be 50 g light — a quarter of the sugar missing. Either pack it as recipes intend, or weigh 220 g per cup.

Swapping icing sugar by volume. A cup of icing sugar weighs 80 g less than a cup of granulated. Volume swaps under-sweeten and dry the bake; convert by weight.

Expecting icing sugar to cream. Powder cannot cut air into butter. Use it where recipes call for it, or give the sponge its lift from well-whipped eggs.

Questions, answered

Is golden caster sugar different?

Slightly: unrefined, with a faint caramel note and the same fine crystals. It swaps for white caster weight for weight in anything.

Can I make caster sugar from granulated?

Yes — blitz granulated briefly in a food processor until finer but not powdery, and let the dust settle before opening. It is a good emergency substitute.

Does brown sugar go off?

It dries out and hardens as its moisture escapes. An airtight jar slows it; a slice of bread in the jar re-softens it overnight.

The short version

Sugars are not interchangeable sweet dust; they are ingredients with grain, moisture and temperament. Learn the four in your cupboard as individuals, weigh them when a recipe crosses between them, and ‘sugar’ in an ingredient list becomes a decision you make rather than a lottery you enter.

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