Brown Sugar (Packed): US cups to kilograms

Brown sugar is a packing-dependent ingredient, which means almost every recipe that calls for it specifies "packed" or "firmly packed" rather than just "1 cup." The difference between packed and loose brown sugar is around forty-seven percent by weight, the largest packing variance of any common baking ingredient, and the reason every published brown sugar recipe takes a position on which method to use.

Packed brown sugar means pressing the sugar firmly into the measuring cup with the back of a spoon or your knuckles, packing it down until it holds the shape of the cup when inverted. Done correctly, a one-cup packed measure of brown sugar will turn out as a dense brown lump on the counter. The official King Arthur figure for this method is 213 grams per US cup. USDA publishes 220, which is essentially the same value within measurement noise.

Loose brown sugar, also called sprinkled or unpacked, runs about 145 grams per cup. This is the figure for sugar spooned into the cup without pressure, the way you would measure flour. Almost no American recipes use this measurement convention. If a recipe says "1 cup brown sugar" without specifying, assume packed. If a recipe is from outside the United States and the sugar is being weighed, the question does not arise.

The single most common conversion mistake with brown sugar is converting a loose volume measurement to a packed weight, or vice versa. A baker reading a metric recipe that calls for 100 grams of brown sugar might pack it down into a cup-and-a-quarter of volume, when the original author had loose sugar in mind. The cookie comes out thirty grams heavier on sugar and the difference is detectable in the final spread and texture. The fix is to weigh the brown sugar and ignore the cup measurement entirely.

Light and dark brown sugar have different molasses contents. Light brown sugar is around three to four percent molasses by weight; dark brown sugar is around six to seven percent. The density difference between light and dark is real but small, around two to three percent. For the calculator, the same 213 gram figure works for both because the molasses content is small relative to the bulk sugar mass. If you are baking a recipe that specifies dark brown sugar and you only have light, you can substitute one for one by weight, but the flavor profile shifts toward less caramel and more sweetness.

The reason packed brown sugar works at all as a measurement system is that the molasses coating gives the crystals a sticky surface, so when you press them together they cohere. Granulated sugar does not pack the same way because dry crystals slip past each other. This is also why hardened brown sugar is so common in kitchens. Once the molasses dries out, the sugar crystals fuse into a brick. You can recover hardened brown sugar by sealing it in a bag with a slice of bread or a damp paper towel for a day, but you cannot recover the original packing density without breaking up the lumps and re-coating them.

Density matters most for brown sugar in recipes that depend on its moisture content as well as its sweetness. American-style chocolate chip cookies, gingerbread, butterscotch sauce, and barbecue rubs all use brown sugar partly for its molasses, which contributes around 0.6 grams of water per gram of sugar. Substituting white sugar one for one by weight will produce a noticeably drier and crispier result. If you must substitute, replace each cup of packed brown sugar with one cup of white sugar plus one tablespoon of molasses, which approximates the original moisture and flavor.

This page defaults to the packed measurement because that is what almost every English-language recipe assumes. The calculator will produce both packed and loose figures if you select the variant from the dropdown.