A standard 1-pound box of brown sugar contains between 2 1/4 and 2 1/2 cups of firmly packed brown sugar, depending on the brand. Larger amounts of brown sugar are usually sold in plastic bags.
Brown sugar is made by separating sucrose from the reduced juice of either sugar cane or sugar beets. Once the sugar crystals have been removed, the resulting liquid is known as molasses, and the sugar crystals are brown sugar, which is also sometimes known as raw or natural sugar. Both substances can be further refined. The raw sugar can be used to produce white sugar and the molasses can be used to extract more sucrose.
Other than raw brown sugar, brown sugar can be made from white sugar by mixing it with some molasses. Because of the molasses that is either added to white sugar or what remains naturally in the less-refined raw sugar, brown sugar has a richer taste and is moister than white table sugar, so it packs more firmly. However, raw sugar is not as moist as light and dark brown sugars. It should be stored in an airtight container to retain its moisture. Light brown sugar is 3.5 percent molasses by weight, while dark brown sugar is 6.5 percent. If a recipe refers simply to brown sugar, then light brown sugar is what it requires.