Kitchen weight conversion
Caster Sugar Cups To Grams Converter
Convert cups of caster sugar to grams using cup size, measuring style, ingredient density and recipe scaling, with rounded baking weights for UK kitchens.
Enter The Cup Measure
Gram Result
Enter cups and cup size to see the gram amount.
For baking, weigh the sugar if you can. Cups are a volume measure, while grams measure mass.
Why Caster Sugar Needs Its Own Conversion
Caster sugar is finer than standard granulated sugar and flows into the spaces of a measuring cup differently. That is why a generic cup-to-gram converter is not good enough for baking. One cup of flour, one cup of chopped nuts and one cup of caster sugar all have the same volume, but they do not weigh the same. Even for sugar, crystal size and measuring style can shift the weight. A level 250 ml metric cup of caster sugar is often treated as about 225 g, while a US customary cup is smaller and comes out closer to 213 g when the same density is used.
This page is made for UK bakers who have found a recipe in cups and want a practical gram value for a kitchen scale. It lets you pick the cup system, adjust density, model a lightly spooned or heaped cup, and scale the recipe at the same time. If the recipe writer gives their own gram equivalent, use that first. If they only give cups, this converter gives a clear starting value and shows the assumptions behind it.
How To Measure Caster Sugar
The most reliable method is to place a bowl on a kitchen scale, tare it to zero, and weigh the gram result directly. If you only have cups, use a dry measuring cup rather than a mug. Fill the cup without pressing the sugar down, then level the top with a straight edge. Do not shake the cup hard, because that settles the crystals and can add extra sugar. A heaped cup is not a standard measure; it depends on the shape of the cup and the hand of the person measuring.
For cakes, biscuits, meringues and custards, sugar affects sweetness, browning, tenderness, moisture and structure. A difference of 20 g may not ruin every bake, but it can matter in a small batch or a recipe with few ingredients. When the converter gives 225 g, weighing 225 g is better than trying to reproduce the exact cup fill that another cook used.
Formula And Method
Millilitres = cups x selected cup volume
Base grams = millilitres x caster sugar density
Adjusted grams = base grams x measuring style multiplier x recipe scale factor
Ounces = grams / 28.3495
The default density is 0.90 g/ml. That is a practical baking assumption rather than a laboratory value. It gives 225 g for a 250 ml metric cup and about 213 g for a 236.588 ml US customary cup. The converter rounds the main answer to the nearest gram because kitchen scales and cup fills are rarely more exact than that. It also shows a rounded “baking value” to the nearest 5 g, which is often the most sensible value to write on a printed recipe card.
Quick Conversion Table
| Caster sugar | Metric cup, level | US customary cup, level | Useful kitchen note |
|---|---|---|---|
| 1/4 cup | 56 g | 53 g | Common for toppings, small sponge layers and buttercream adjustments. |
| 1/3 cup | 75 g | 71 g | Round to 75 g unless the recipe is very small. |
| 1/2 cup | 113 g | 106 g | For most bakes, 110 g is a practical rounded value. |
| 2/3 cup | 150 g | 142 g | Check the recipe origin before choosing the cup size. |
| 3/4 cup | 169 g | 160 g | Useful for cakes where the recipe may also list butter in cups. |
| 1 cup | 225 g | 213 g | A UK or Australian cup-style recipe often points toward the metric cup value. |
| 2 cups | 450 g | 426 g | Large differences become more visible as the recipe scales up. |
Worked Recipe Examples
Victoria sponge from a metric-cup recipe
A recipe asks for 1 cup caster sugar and appears to be Australian or metric. Select metric cup, level fill and the default density. The result is 225 g. If making half the recipe, set target servings to 0.5 and use about 113 g.
US cookie recipe
A US recipe lists 3/4 cup caster or superfine sugar. Select US customary cup and level fill. The result is about 160 g. If the cookies spread too much, check butter temperature before changing sugar.
Heaped cup from an old family note
If a handwritten note says “heaped cup”, select heaped cup only as an estimate. The result is deliberately higher. For repeat baking, weigh the amount you use and write that gram value on the recipe.
Metric, US And Imperial Cups
A cup is not a single worldwide unit. Many modern metric recipes use 250 ml. US customary cups are about 236.588 ml. A US legal nutrition cup is 240 ml. Older British references may use an imperial breakfast cup, which is larger again. The converter includes these options because the source of the recipe matters. A cup of caster sugar from a 250 ml cup can be more than 10 g heavier than the same level sugar in a US customary cup before any measuring-style difference is added.
When A Cup Conversion Can Mislead
Be careful when the recipe is very small, when sugar is central to the structure, or when the recipe also uses egg whites, gelatine, caramel, jam setting or meringue. In those cases, a few grams can affect texture. Also be cautious when swapping caster sugar for granulated sugar, icing sugar or golden caster sugar. They can behave differently in mixing and dissolving even when the gram weight is close. If the recipe gives grams and cups, use the grams and treat the cup measure as a guide.
FAQs
How many grams is 1 cup of caster sugar?
With this converter’s default 0.90 g/ml density, 1 metric cup is 225 g and 1 US customary cup is about 213 g. Some recipe charts use 200 g or 225 g, so check the recipe origin where possible.
Is caster sugar the same as superfine sugar?
In many US recipes, superfine sugar is the closest term to UK caster sugar. It is finer than standard granulated sugar and dissolves faster, which is why it is common in cakes, meringues and drinks.
Should I pack caster sugar into the cup?
No. Caster sugar is normally measured level, not packed. Packing or shaking the cup can add more sugar and change the bake.
Why does the answer change when I select a different cup?
The cup volume changes. A metric cup is 250 ml, while a US customary cup is about 236.588 ml. The same ingredient density gives different grams from different volumes.
Can I use this for granulated sugar?
It is tuned for caster sugar. Granulated sugar is close but not identical. For precise baking, use a page or chart for the exact sugar type named in the recipe.
Sources
- Good Food. (2026). Conversion guides. https://www.bbcgoodfood.com/conversion-guides
- King Arthur Baking Company. (2026). Ingredient Weight Chart. https://www.kingarthurbaking.com/learn/ingredient-weight-chart
- National Institute of Standards and Technology. (2008). Guide for the Use of the International System of Units (SI), Special Publication 811. https://www.nist.gov/pml/special-publication-811
- Bureau International des Poids et Mesures. (2026). The International System of Units (SI Brochure). https://www.bipm.org/en/publications/si-brochure/
Last reviewed: 14 May 2026.