Sugar Conversions: White, Brown, and Powdered

Of all the ingredients on this site, sugar is the one where people most often assume "a cup is a cup" regardless of type. It isn't, and the gap between the different sugars is bigger than you'd think — a cup of powdered sugar weighs barely half what a cup of packed brown sugar does.

The Numbers

Why Powdered Sugar Is So Much Lighter

Powdered sugar is granulated sugar ground down to a fine powder and mixed with a small amount of cornstarch to prevent clumping. Grinding it that fine introduces a lot more air between particles than you get with granulated crystals, which is the whole reason the same cup holds so much less of it by weight — 120g versus 200g for granulated, nearly a 40% difference.

Packed vs Loose Brown Sugar — Why It Matters So Much

Brown sugar clumps naturally because of its molasses content, and recipes are almost universally calibrated assuming you've packed it firmly into the cup with your fingers or a spoon, pressing until it holds the cup's shape when turned out. Unpacked (just scooped loosely), the same cup can weigh 25% less — which, in a cookie recipe, changes both sweetness and texture more than most people expect.

If a recipe just says "1 cup brown sugar" with no other detail, assume packed. It's the default in the vast majority of published recipes.

Superfine (Caster) Sugar

Superfine sugar, also called caster sugar in UK recipes, has finer crystals than standard granulated but weighs almost the same per cup — the crystal size difference isn't large enough to meaningfully change the packing density. You can generally treat granulated and superfine as interchangeable by weight, even though they're not identical in texture.

Substituting Between Sugar Types

Substituting by weight (grams) rather than volume (cups) is always the safer choice if you're out of one sugar type and need to sub in another — otherwise you can end up with noticeably more or less sweetness and moisture than the recipe intended, especially swapping powdered sugar for granulated or vice versa.

A Worked Example

A recipe calls for 1½ cups packed brown sugar and you only have loose, un-packed brown sugar in the bag. At 220g per packed cup, 1½ cups = 330g. You should weigh out 330g regardless of how many "cups" that ends up filling loosely — the weight is what the recipe actually needs, not the volume.

FAQ

Can I make my own powdered sugar from granulated?
Yes — granulated sugar blended finely in a food processor or blender with a small amount of cornstarch approximates powdered sugar reasonably well in a pinch.

Does light vs dark brown sugar change the conversion?
Not meaningfully — the molasses content differs slightly between light and dark brown sugar, but the weight-per-cup figure is close enough to treat them the same for conversion purposes.

Why do some recipes list sugar in grams already?
Recipes originating outside the US, or written by professional bakers, often default to weight because it removes exactly this kind of ambiguity.

For the rest of your dry ingredients, see cups to grams, or convert any amount directly with the tool.