Butter Converter (Sticks, Tablespoons, Cups, Grams & Ounces)

American butter is legally required to contain only 80% milkfat, leaving 16% to 18% water. European-style butter (Kerrygold, Plugrá, President) contains 82% to 84% milkfat and only 14% to 16% water. Substituting American butter into French pastry recipes injects excess water, which activates flour gluten and ruins the delicate lamination of croissants and puff pastry.

Commercial salted butter contains between 1.5% and 2.0% salt by weight—equal to approximately 1/3 to 1/2 teaspoon of salt per stick (1.8g to 2.2g). If a recipe calls for unsalted butter plus added salt, using salted butter doubles the sodium content, creating an unpleasantly salty profile in sweet frostings and cookies.

Both packages weigh exactly 113.4 grams (1/2 cup), but their shapes differ completely. East Coast "Elgin" sticks are long and slender (4.75" × 1.25"), while West Coast "Western" sticks are short and stubby (3.1" × 1.5"). Measuring butter visually by cutting an inch off the stick will cause a 35% measurement error if you use the wrong regional pack.

Cold stick butter has a physical bulk density of approximately 0.96 g/mL. When melted, butter expands thermally and separates into clear butterfat (0.89 g/mL) and dense water/milk solids. 1 cup of melted butter poured into a measuring cup yields less total mass than 2 solid sticks packed firmly into the same cup.

1 American stick of butter is labeled "4 oz" (weight, 113.4 grams), and is simultaneously equal to 1/2 cup (which holds 4 fluid ounces of volume). Because butter's density is very close to water (0.96 vs 1.00), many bakers mistakenly assume dry ounces and fluid ounces are interchangeable across all ingredients, leading to disasters when measuring flour or honey.