How to convert water
Our reference is 236.5882 grams per US reference cup of water, liquid water; approximate room-temperature kitchen density of 1 g/ml. That works out to about 1 grams per millilitre, so cups = grams ÷ 236.5882 and grams = cups × 236.5882 in US customary measures.
For metric and Australian recipes the cup holds 250 ml, so one cup of water is about 250 grams. Australian tablespoons hold 20 ml rather than 15 ml, which the calculator handles when you pick that system.
Preparation changes the weight
The reference describes water as: liquid water; approximate room-temperature kitchen density of 1 g/ml. A different form, such as sifted, packed, melted, chopped or cooked, can hold a different weight in the same cup and needs its own reference. When a recipe gives a gram amount, weigh that amount instead of converting.
Brand, moisture and how firmly the cup is filled all move the practical result. Treat the numbers here as recipe equivalents, not laboratory densities.
Where the number comes from
The reference comes from US Geological Survey water density, which lists 1 mL as 1 grams. Approximate water density of 1 g/mL, not a universal rule for liquids. This site assigns the published cup weight to its adopted US reference cup of 236.5882365 ml; the source itself does not define an exact millilitre cup volume. Checked September 25, 2026.