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Not All Sugar Weighs the Same: 125 g to 220 g per Cup
« One cup of sugar » spans almost 100 g depending on which sugar is in the jar. Four measured densities explain why — and why swapping sugars by volume quietly rewrites the recipe.
Four sugars, four densities
The same US cup weighs out very differently depending on the crystal.
- Powdered sugar (0.53 g/ml): about 125 g per US cup
- Coconut sugar (0.76): about 180 g
- Granulated sugar (0.845): about 200 g
- Brown sugar, packed (0.93): about 220 g
Granulated is the reference point
At 0.845 g/ml with a fill variance of ±5 %, granulated sugar is one of the more honest ingredients in a cup: the crystals are uniform, they flow, and they barely compress. One US cup lands near 200 g — which is why so many conversion charts quietly treat that figure as the definition of « a cup of sugar ».
Brown sugar: the only cup you pack on purpose
Brown sugar carries molasses — roughly 10 % of its mass — which leaves it damp and clumpy. Recipes say « packed » because an unpacked cup traps air between the clumps; pressed down it reaches 0.93 g/ml, about 220 g per US cup, ±7 %. The order to pack repairs a measurement that would otherwise mean nothing.
Powdered sugar: the least trustworthy cup in the pantry
Powdered sugar is ground fine enough to behave like flour — it bridges, compacts and holds air. Sifted, it fluffs toward 0.4 g/ml; packed into the cup it can nearly double. The measured figure — 0.53 g/ml, about 125 g a cup — already carries ±8 % variance, and recipes that say « sifted » mean yet another weight. Weigh it.
Coconut sugar and the swap trap
Coconut sugar granulates coarser and darker than white sugar, at 0.76 g/ml — about 180 g a cup, ±8 %. Swapping it cup-for-cup for granulated removes roughly 10 % of the sweetener by weight; gram-for-gram, the swap is clean. The same rule protects the reverse swap.
The rule that survives every jar
Convert each sugar by its own density — that is what the converters on this site do — and weigh whenever the sugar can hold air, which means anything finer or wetter than granulated. And never convert between sugars by volume: 220 g of packed brown sugar in a cup is not the same sweetness as 125 g of powdered.