Sweetened condensed milk

One US cup of sweetened condensed milk weighs 306 grams. Going the other way, 100 grams is about 0.33 cups.

Sweetened condensed milk is regular milk with about 60 percent of the water evaporated off and sucrose added at 40 to 45 percent by weight. The result is a thick, syrup-like product that behaves in a measuring cup more like honey or maple syrup than like milk. It should not be confused with evaporated milk, which is the same milk-reduction process without the added sugar.

USDA FoodData Central publishes 1 cup at 306 grams and 1 tablespoon at 19 grams (FDC 171275, Milk, canned, condensed, sweetened, SR Legacy). This gives a bulk density of 1.2934 grams per millilitre. King Arthur's ingredient weight chart publishes 1/4 cup at 78 grams, which extrapolates to 312 grams per cup and 1.3187 grams per millilitre. The two figures agree within 1.9 percent, comfortably inside the 5 percent tolerance we apply to the syrup category.

We publish the USDA figure of 306 grams per cup because it comes with the underlying tablespoon and 100-gram numbers rather than an extrapolation from a partial cup.

The unusually high density comes from the composition: after evaporation and sugar addition, the product is roughly 27 percent water, 55 percent sugar, 8 percent fat and 8 percent protein by weight. Sugar dissolved in water makes a denser solution than water alone, and the concentrated milk solids add more density on top. The final product weighs about 1.3 times more per volume than water.

Standard US cans of sweetened condensed milk are labelled 14 ounces, which is 397 grams by weight (14 × 28.35). That corresponds to about 1.30 cups by volume at the USDA density. Most recipes that call for 'one can' intend the full 397 grams regardless of what the volume conversion says. When a recipe calls for 1 cup and no can is specified, weigh out 306 grams.

Evaporated milk is a related but very different product: same milk reduction, no added sugar. Evaporated milk weighs about 252 grams per cup and has a density of 1.065 grams per millilitre — closer to whole milk than to sweetened condensed milk. The two are not interchangeable in recipes. Dulce de leche is sweetened condensed milk that has been cooked further until the sugars caramelise, and its density is slightly higher because of additional water loss during cooking.

The FDA identity standard for sweetened condensed milk is at 21 CFR 131.120, requiring at least 8 percent milkfat and 28 percent total milk solids in the sugared product. The Codex Alimentarius standard CXS 282-1971 covers evaporated milks and sweetened condensed milks internationally with similar minimums. Neither standard specifies a density; both address composition to protect the product name. Because the composition is regulated, brand-to-brand variation in density is small — Nestle Eagle Brand and store-brand condensed milks measure essentially the same by weight at the same volume.

The category here is 'syrup' rather than 'liquid' because sweetened condensed milk's measuring behaviour matches other concentrated sugar solutions: thick, slow-pouring, and not sensitive to how the cup is filled once it settles. The 5 percent syrup tolerance applies, and both sources sit well inside it.