Brown sugar

One US cup of brown sugar weighs 220 grams (7.8 ounces). Going the other way, 100 grams is about 0.45 cups.

Also called light brown sugar, dark brown sugar, soft brown sugar.

Sugars compared: cup weights side by side, the source behind each, and why they differ.

A cup of firmly packed brown sugar weighs 220 g (7.8 oz), a density of 0.93 g/mL. USDA weighs a packed cup at 220 g and King Arthur at 213 g, within 4% of each other. Loosely spooned, the same sugar weighs about a third less, 144 g by USDA's measure, which is why recipes say packed.

Brown sugar is white sugar coated with molasses, less for light brown and more for dark, or a partly refined cane sugar that keeps some of its own. The molasses film makes the crystals soft and sticky, so they press together when pushed into a cup and hold the cup's shape when tipped out. Light and dark brown sugar weigh the same by the cup; King Arthur gives one figure for both, and the difference is flavour and colour.

USDA's Standard Reference record for brown sugar (FDC 168833) gives 1 cup packed as 220 g and 1 cup unpacked as about 144 g. King Arthur's ingredient weight chart lists brown sugar, dark or light, packed, at 1 cup = 7 1/2 oz = 213 g. The two packed figures are 3.3% apart, inside the 5% this site allows for sugars, and USDA's 220 g is published.

The unpacked figure is not published as a separate state because USDA is the only source that measures it. America's Test Kitchen tested packed against loosely filled cups with ten cooks and found the packed cup about 2 ounces heavier on average, the same direction as USDA's 76 g gap, but it published the difference rather than a cup weight. Converter sites give unpacked brown sugar anywhere from 130 to 180 g per cup without saying where the numbers came from.

The physical check: sucrose crystals weigh 1.59 g/mL, and granulated sugar fills about 53% of a cup at 200 g. Packing pushes brown sugar's softened crystals together until they fill about 58% of the cup, 220 g, while loosely spooned brown sugar clumps and bridges and fills only about 38%, 144 g. No other sugar on this site changes so much with how the cup is filled.

Practical guidance: when a recipe says brown sugar, it means packed. Press it into the cup firmly enough that it holds its shape when turned out, and use 220 g per cup, 110 g per half cup, 55 g per quarter cup and 14 g per tablespoon. Hard, dried-out brown sugar packs differently and should be softened first or weighed. Muscovado, a darker unrefined sugar, weighs 200 to 235 g per packed cup on this site.