Half-and-half

One US cup of half-and-half weighs 242 grams (8.5 ounces). Going the other way, 100 grams is about 0.41 cups.

One cup of half-and-half weighs 242 grams (1.023 g/mL), landing between whole milk (denser, because milk solids raise density) and heavy cream (lighter than water, because 35% fat pushes density down). King Arthur Baking's chart lists 227 g per cup for 'cream (heavy cream, light cream, or half & half)' — the classic fluid-ounce error, undercounting by 6.6% and treating three different-density products as interchangeable.

The FDA defines half-and-half as a homogenized blend of milk and cream containing 10.5-18% milkfat (21 CFR § 131.180). Every mass-market US product anchors at the low end, 10.5-12%, because 'light cream' occupies the 18-30% band as a separate FDA product category. So while the legal window is wide, real cartons converge on 10.5-12%, which is what USDA measured for FDC 171255: one cup is 242 grams, one tablespoon is 15.1 grams, density is 1.023 g/mL.

King Arthur's 227 g/cup is 8 fluid ounces treated as 8 mass ounces (8 × 28.35). This is the fluid-oz-as-mass-oz confusion the ExactCups project exists to correct. The physical density of half-and-half is slightly above water — not below — because milk solids (protein, lactose, minerals) outweigh the density-lowering effect of 10-12% fat. Actual density is 1.023 g/mL, not 0.96 g/mL. Beyond the numeric error, KA groups heavy cream (35% fat), light cream (18-30% fat), and half-and-half (10.5-12% fat) under one entry — but each has a distinct density because fat is less dense than water. Heavier cream runs lighter per cup; leaner half-and-half runs heavier. Averaging them is not physically meaningful for weight-based conversion.

Producer labels converge with USDA once rounding is factored in. Land O'Lakes Traditional Half and Half and Organic Valley Organic Half & Half both list a 2 Tbsp serving (30 mL) at 30 grams, rounding density to 1.000 g/mL — the standard dairy nutrition-label convention, which quantizes mass and volume to whole numbers for legibility. That reads out to 236.6 g/cup, within 2.3% of USDA. Under the 5% liquid category tolerance, USDA and producer labels are convergent, and 242 is the published single figure.

Practical bakers: the difference matters most where a recipe depends on fat-to-liquid ratio. Custards, pastry cream, ganache, panna cotta, and ice cream bases need the true mass. Using King Arthur's 227 g/cup in a panna cotta shorts you 15 grams per cup of half-and-half; the result sets softer or fails to set. Ganache with too little cream by weight breaks. Ice cream with too little fat freezes coarse.

For coffee and casual pouring, none of this matters — the label rounding is what your carton reflects and the difference is under a spoonful. For volumetric substitution, half-and-half and whole milk swap cleanly by cup (density difference is under 1%), though the fat content still changes browning, set, and mouthfeel. Substituting for heavy cream is where the difference bites: cream is fattier and lighter per cup, so a volumetric swap thins the result AND under-delivers fat. Weigh both.

Ultra-pasteurization, lactose-free processing (Land O'Lakes Lactose-Free), and added stabilizers like sodium citrate or carrageenan do not measurably shift density. Grassmilk and organic labeling do not either. The 242 g/cup figure holds across mass-market US half-and-half.

The following published figures for half-and-half are rejected here, with the physics or standards reasoning behind each rejection on its own page:

• King Arthur Baking Ingredient Weight Chart: 227 g per cup