Cooking Conversions

One cup of all-purpose flour weighs about 125 grams. One cup of granulated sugar weighs about 200 grams. One cup of honey weighs about 340 grams. Same volume, wildly different weights. This is the central problem of cooking conversion: volume and weight are not interchangeable unless you know the density of what you are measuring.

Professional bakers weigh ingredients in grams rather than scooping with cups, and for good reason. The amount of flour in "one cup" varies by 20% or more depending on whether it was scooped, spooned, or sifted into the measuring cup. King Arthur Baking Company tested this and found that a scooped cup of flour averages 140g while a spooned-and-leveled cup averages 120g. That 20-gram difference in a recipe calling for 3 cups of flour changes the flour-to-liquid ratio enough to produce noticeably denser bread or drier cake. Weight measurement eliminates this variability entirely.

The problem gets worse when converting between American and non-American recipes. American recipes measure nearly everything by volume (cups, tablespoons, teaspoons), while recipes from Europe, Australia, and most professional bakeries specify weights in grams. A recipe calling for "200g butter" requires a conversion that accounts for butter's density (about 911 g per liter, or roughly 227g per cup). Simply converting 200g to "some number of cups" without knowing the ingredient produces garbage results.

The US customary volume system follows exact ratios: 1 cup = 16 tablespoons = 48 teaspoons = 8 fluid ounces. One US cup equals 236.588 milliliters (derived from the gallon, 3,785.411784 ml divided by 16). These volume-to-volume conversions are straightforward. The complexity enters when crossing between volume and weight, which requires per-ingredient density data.

Liquid ingredients add another layer of complexity. Water, milk, and thin liquids weigh close to 1 gram per milliliter (water is exactly 1 g/ml at 4 degrees C), so volume-to-weight conversion is straightforward. But oils are lighter (about 0.92 g/ml for vegetable oil), and syrups are heavier (maple syrup runs about 1.32 g/ml). Honey is denser still at roughly 1.42 g/ml. A tablespoon of honey weighs about 21 grams, while a tablespoon of water weighs about 15 grams. Substituting one sweetener for another without adjusting for density changes both the weight and the liquid ratio of the recipe.

The metric-to-US volume conversions themselves follow exact ratios: 1 US cup = 236.588 ml (derived from the definition of the US gallon as 3,785.411784 ml, divided by 16). One tablespoon = 14.787 ml. One teaspoon = 4.929 ml. These are the US customary definitions; Australian tablespoons are 20 ml, and UK tablespoons are 17.758 ml. This converter uses US definitions unless otherwise specified.

This converter handles 9 units: cups, tablespoons, teaspoons, fluid ounces, and milliliters on the volume side, plus grams, ounces, pounds, and kilograms on the weight side. For volume-to-weight and weight-to-volume conversions, it draws on density data for over 60 ingredients sourced from USDA FoodData Central. Each ingredient has specific grams-per-cup, grams-per-tablespoon, and grams-per-teaspoon values. Selecting the correct ingredient before converting is what makes the result accurate.