Caster sugar grams to cups
To convert grams to cups, divide the grams by 200. For example, 100 g of caster sugar ≈ ½ cup (0.5 cups).
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Caster sugar is superfine granulated sugar, common in UK and Australian recipes. A US cup weighs 200g, the same as regular granulated, because the smaller crystals settle into nearly identical packing. This page converts caster sugar grams to cups for creaming, meringues, and delicate batters.
Caster sugar grams to cups chart (US cup)
| Grams | Cups (approx.) | Decimal cups |
|---|---|---|
| 25 g | ⅛ cup | 0.12 |
| 50 g | ¼ cup | 0.25 |
| 75 g | 0.38 cup | 0.38 |
| 100 g | ½ cup | 0.5 |
| 125 g | 0.62 cup | 0.62 |
| 150 g | ¾ cup | 0.75 |
| 175 g | ⅞ cup | 0.88 |
| 200 g | 1 cup | 1 |
| 250 g | 1¼ cups | 1.25 |
| 300 g | 1½ cups | 1.5 |
| 400 g | 2 cups | 2 |
| 500 g | 2½ cups | 2.5 |
Why caster sugar weighs what it does
Caster sugar's crystals are roughly half the size of standard granulated, but the sugar itself is the same pure sucrose at the same crystal density, so a cup still lands at about 200g. The finer grains pack the gaps between larger ones slightly more efficiently, yet the difference is within measuring noise. Where it does shift is moisture and clumping: caster left in a humid pantry absorbs water and weighs marginally heavier per cup, and golden (unrefined) caster runs a touch denser than white.
How to measure caster sugar
Stir the caster first to break any humidity clumps, then spoon it into the cup and level with a straight edge. Don't tap or pack it; caster compacts more readily than coarse sugar, and a few firm taps can add 10 to 15g. For meringues and creaming, weighing to 200g per cup is far more reliable than scooping.
Common mistake
Assuming caster and powdered (icing) sugar are interchangeable because both look fine. They are not: powdered sugar contains cornstarch and weighs only about 120g per cup, so swapping cup-for-cup throws a recipe off badly. Caster matches granulated by weight, not the sugars sold as confectioners'.
Other cup sizes
| Cup type | 1 cup of caster sugar |
|---|---|
| US cup (240 ml) | 200 g |
| Metric cup (250 ml) | 208 g |
| Australian / South African cup (250 ml) | 208 g |
| Imperial cup (284 ml) | 237 g |
Where it matters
Caster sugar shines where fast dissolving matters: meringues, pavlova, sponge and Victoria cakes, mousses, and creamed butter mixtures that need a smooth, grit-free finish. In these, the 200g-per-cup conversion lets you follow American volume recipes precisely, or scale a British metric recipe without guessing how the finer crystals affect the cup.
FAQ
Is caster sugar the same weight as granulated sugar per cup?
Yes. Both are about 200g per US cup. The crystal size differs, but the density of the sugar itself is the same, so the weights match.
Can I substitute caster sugar for granulated 1:1?
By weight and by volume, yes. Caster simply dissolves faster, which is an advantage in meringues and creaming but makes no difference to the conversion.
How many cups is 200g of caster sugar?
Exactly 1 US cup, at 200g per cup. So 100g is half a cup and 400g is 2 cups.
Is caster sugar the same as powdered or icing sugar?
No. Powdered (icing/confectioners') sugar is ground to a powder and contains anti-caking starch, weighing only around 120g per cup. Caster is fine granulated and weighs 200g per cup.