Not every liquid behaves like water. Heavy whipping cream, buttermilk, sweetened condensed milk, and modern plant-based milks (such as oat, almond, and soy) exhibit varying specific gravities.
A cup and a quarter of whole milk registers 10 fluid ounces on a liquid jug and weighs roughly 10.6 dry ounces on a digital scale due to dissolved milk solids and butterfat. Plant milks with added gums or starches track closely to whole dairy, averaging around 10.4 to 10.5 ounces for 1 1/4 cups. Honey and maple syrup introduce extreme shifts: 1 1/4 cups of pure maple syrup weighs roughly 14.1 ounces, while clover honey tops 17.5 ounces.
When professional recipe developers publish formulas for custards, ice cream bases, or potluck sides, like those popularized by America's Test Kitchen, they specify liquid ingredients in fluid ounces or milliliters to prevent sticky miscalculations. Pouring heavy syrups into dry measuring cups creates significant residue loss along the sidewalls, robbing the batter of critical moisture.
