Molasses

One US cup of molasses weighs 337 grams. Going the other way, 100 grams is about 0.30 cups.

Molasses is the thick dark syrup left over when sugar cane or sugar beet juice is boiled and the sucrose crystallises out. What is drained from the crystals is molasses. It is one of the densest liquids in a home kitchen — mostly sugar dissolved in a small amount of water, with the concentrated minerals from the original cane juice.

USDA FoodData Central publishes 1 cup at 337 grams and 1 tablespoon at 20 grams (FDC 168820), giving a bulk density of 1.4244 grams per millilitre. King Arthur's ingredient weight chart publishes 1/4 cup at 85 grams, which extrapolates to 340 grams per cup and 1.4371 grams per millilitre. The two figures agree within one percent, comfortably inside the 5 percent tolerance we apply to the syrup category.

We publish the USDA figure of 337 grams per cup because it comes with the underlying tablespoon and 100-gram numbers rather than an extrapolation from a partial-cup measurement.

Molasses has three commercial grades that come from successive stages of the sugar-refining boil. Light or mild molasses, sometimes called first molasses, is drained after the first crystallisation and is the sweetest and lightest in colour. Dark or full-strength molasses, the second boil, is thicker, less sweet, and more strongly flavoured. Blackstrap molasses, the third boil, is nearly bitter, very dark, and highest in minerals; it is roughly 42-45 percent water rather than 22 percent, so its density is slightly lower than the USDA figure — closer to 1.35 grams per millilitre. USDA's generic molasses entry sits between light and dark grades and is a good default. For blackstrap specifically, weigh rather than measure by volume if the recipe is sensitive.

Molasses is often confused with three related products. Treacle in British usage covers a range from light (golden syrup, thinner and lighter than molasses) to black treacle, which is the closest to American molasses. Sorghum syrup is made from sorghum cane and is thinner, sweeter, and less mineral-heavy than sugar-cane molasses. Golden syrup is a light amber inverted-sugar syrup with no cane-refining residues, similar in density but very different in flavour. None of the three substitute one-for-one for molasses by taste or mineral content, though they measure similarly.

Brown sugar is granulated white sugar with molasses added back in. Light brown sugar is roughly 3-4 percent molasses by weight; dark brown sugar is roughly 6-8 percent. Recipes that call for brown sugar and molasses together already account for the small amount of molasses that is in the brown sugar.

The FDA has no identity standard for molasses; the term is understood by common usage rather than by regulation. The Codex Alimentarius standard for sugars (CXS 212-1999) covers refined and unrefined sugars but does not address molasses as a separate product.

The category here is 'syrup' rather than 'liquid' because molasses is a highly concentrated sugar solution and its measuring behaviour matches honey, maple syrup and corn syrup — very dense, slow to pour, and not sensitive to how the cup is filled once it settles. The 5 percent syrup tolerance applies. A cup of molasses weighs about 2.4 times more than a cup of water.