Sucrose milled to a grain roughly half the size of granulated sugar. Still crystalline and free-flowing, but it dissolves far faster.
What it does in a recipe: Sweetness that dissolves quickly and completely — essential for meringue, delicate creamed cakes and cold drinks. Pick the swap that covers that job — the ratios below are written so you can act on them without doing any arithmetic.
Also called: Superfine sugar, Baker's sugar, Berry sugar
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Granulated sugar, blitzed
1 cup caster sugar = 1 cup granulated sugar, pulsed in a food processor
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4 ways to replace caster sugar
Granulated sugar, blitzed
Closest match
1 cup caster sugar = 1 cup granulated sugar, pulsed in a food processor
Caster sugar is only granulated sugar ground smaller, so a short blitz produces the real thing rather than an approximation.
MethodPulse in 5-second bursts for 15-20 seconds total. Stop before it goes cloudy and powdery — overground sugar behaves like powdered sugar and will not whip a meringue properly.
Trade-offNone worth mentioning if you stop at the right point. Measure after grinding, since the volume settles slightly.
Identical sucrose at identical sweetness per cup — only the dissolving speed differs, and extra time or heat can make up for it.
MethodCream with butter for an extra minute or two, and in a meringue add it more slowly and keep whisking until a pinch rubbed between your fingers feels smooth.
Trade-offMeringues and mousses risk a gritty texture or weeping if the crystals never fully dissolve. In a cold drink it simply sinks to the bottom.
1 cup caster sugar (200 g) = 200 g powdered sugar, about 1 3/4 cups by volume
The same sucrose by weight, which is why you must weigh rather than scoop — powdered sugar is far bulkier per cup.
Trade-offThe cornstarch in powdered sugar softens meringue structure and can leave a chalky note, and creamed cakes come out finer and denser with less lift.
1 cup caster sugar = 1 cup packed light brown sugar
Comparable sweetness per cup with a fine, damp grain that dissolves reasonably well into batters.
Trade-offColours the batter and adds caramel flavour, which rules it out for a pale sponge or a white meringue. The extra moisture also makes the crumb denser.
UK caster sugar and US superfine sugar are the same product under different names. Neither is interchangeable with icing or confectioners' sugar, despite how often recipes blur them.
Cooking around an allergy? Diet tags here describe the ingredient itself, not any particular brand. Processed products change formulation without notice and shared production lines are common, so read the label on everything you use. A severe allergy is a medical matter — confirm with the manufacturer or your clinician rather than relying on a substitution chart.