A cooking converter changes recipe measures between the weight and volume units kitchens use around the world — grams to cups, millilitres to tablespoons, or teaspoons to millilitres. It exists because recipes are written two incompatible ways: most of the world weighs ingredients in grams, while American recipes measure them by volume in cups and spoons.
The formula and its one big caveat. Weight and volume are different quantities, so bridging them requires a density. This converter uses the water basis, where 1 millilitre of water weighs exactly 1 gram. On that basis 1 US cup = 236.59 mL = 236.59 g, 1 tablespoon = 14.79 mL, 1 teaspoon = 4.93 mL and 1 US fluid ounce = 29.57 mL. That is exact for water, milk, stock and most thin liquids — but not for dry ingredients. A cup of all-purpose flour is about 120 g, not 237 g, because flour is far less dense than water; a cup of granulated sugar is about 200 g and a cup of honey about 340 g.
Worked example. A recipe calling for 250 mL of milk needs 250 g on a kitchen scale, or a little over one US cup (250 ÷ 236.59 ≈ 1.06 cups). Three tablespoons of olive oil is 3 × 14.79 ≈ 44.4 mL. And 500 mL of stock is roughly 2.1 cups.
Where it's used. Following American recipes outside the US, or European and Indian recipes inside it, is the main case — and the volume-to-weight caveat above is why serious baking recipes give grams. Cup sizes are not even universal: a US cup is 236.6 mL, an Australian metric cup is 250 mL, and a British recipe cup is usually 250 mL too, so a "cup" can vary by about 6% before you account for density at all. For liquids this converter is exact; for flour, sugar and other solids, weigh where you can.