Granulated Sugar: ounces to US cups

Granulated sugar looks deceptively uniform in the bag, but the crystals are surprisingly mobile, sliding past each other with very little friction and almost no clumping. Each crystal is a hard, faceted cube of sucrose roughly 0.5 mm across, dense in itself (sucrose is 1.59 g/cm³ as a pure crystal) but separated by enough air space that a level cup weighs only about 198 grams according to the King Arthur Baking ingredient weight chart, putting the bulk density at 0.8369 g/ml. That means well over 40 percent of the volume in your measuring cup is air between crystals, and how those crystals settle is what makes the conversion finicky. Tap the cup on the counter and the crystals shift downward, fractions of a millimeter at a time, until you have meaningfully more sugar in the same nominal volume. Unlike flour, sugar will not compress dramatically under a heavy hand, but unlike water, it will not self-level either. It sits wherever you put it, which is exactly the problem.

The most common mistake is scooping straight from the bag or canister and assuming you have a level cup. When you plunge a measuring cup into a deep bag of granulated sugar, the cup compacts the crystals against the bag wall and against each other, and you pull up a cup that can easily weigh 215 to 220 grams instead of 198. That is roughly a 10 percent overshoot, and in a recipe written by weight in a serious baking book, it is the difference between a tender cake and one that browns too aggressively, spreads too far, or develops a crackly sugary crust where you wanted a soft top. People rarely suspect sugar of misbehaving because it pours so cleanly, but the scooping motion itself is the error.

The right technique is the same one good bakers use for flour, adapted for sugar's behavior. Stir the sugar in the canister first to break up any settling from shipping or storage, then spoon it loosely into your dry measuring cup until the cup is heaped slightly above the rim. Sweep the excess off level with the flat back of a knife or a bench scraper in a single pass. Do not tap, do not shake, do not press. If you own a kitchen scale, skip the cup entirely and weigh out 198 grams per US cup called for in the recipe; this is the value King Arthur publishes, and it is what most American recipe developers are targeting whether they say so or not.

Density precision matters most in three categories. First, caramel and candy work, where the sugar to water ratio determines the cooking temperature curve and the final texture; an extra 20 grams of sugar in a soft-ball-stage caramel can push it firm or hard and change the chew entirely. Second, meringues, macarons, and Italian buttercreams, where the sugar syrup ratio to egg whites controls structure and stability; too much sugar and the foam weeps, too little and it collapses. Third, cookies, where sugar drives both spread and surface crackle through its melting and recrystallization behavior in the oven; an overscooped cup of sugar in a chocolate chip cookie batch produces flatter, crunchier, more deeply browned cookies than the recipe intended, and bakers blame the butter or the flour when the sugar was the culprit.

Substitution within the white-sugar family is straightforward by weight, less so by volume. Caster sugar (the UK term for superfine sugar) has the same chemistry but smaller crystals that pack more tightly, so a cup of caster sugar weighs closer to 225 grams; substitute one for one by weight, never by volume. Powdered sugar is granulated sugar that has been milled to a fine powder and cut with about 3 percent cornstarch, which makes it a non-substitute in most baking applications because the cornstarch changes the structure. Brown sugar carries 3 to 5 percent molasses and 1 to 2 percent moisture, which adds flavor and acidity, and swapping it for granulated will change browning, spread, and crumb. Turbinado and demerara have larger, harder crystals that do not dissolve as readily and belong on top of muffins, not folded into batters where granulated was specified.