Recipes measure liquids in two ways: by volume (ml, cups, spoons, fluid ounces) and by weight (grams and ounces). Here is what each unit means, which ones differ between countries, and when to use which.
Volume measures how much space a liquid takes up. Weight measures how much of it there is. For water-based liquids the two are almost the same number, which is why volume measuring works so well for milk, stock and juice. For oil, honey and syrup they diverge, because a cup of honey weighs about 40 percent more than a cup of water. Knowing which unit a recipe means, and when to switch, is most of the skill.
| Unit | US | UK imperial | Metric |
|---|---|---|---|
| Teaspoon | 4.93 ml | 5 ml (metric spoon) | 5 ml |
| Tablespoon | 14.79 ml | 15 ml | 15 ml (20 ml in Australia) |
| Fluid ounce | 29.57 ml | 28.41 ml | not used |
| Cup | 236.59 ml (label cup 240 ml) | about 284 ml in old recipes | 250 ml |
| Pint | 473.18 ml (16 fl oz) | 568.26 ml (20 fl oz) | not used |
| Quart | 946.35 ml | 1.137 l | not used |
| Gallon | 3.785 l | 4.546 l | not used |
| Millilitre and litre | 1 l = 1,000 ml, the same everywhere | ||
Metric recipes use millilitres and litres almost exclusively, plus 5 ml and 15 ml spoons. US recipes use teaspoons, tablespoons, fluid ounces and cups. Older British recipes use imperial pints and fluid ounces, which is where most mix-ups begin. A UK pint is 20 fluid ounces and a US pint is 16, so the two pints differ by about 20 percent.
Weight is measured in grams and kilograms in metric countries, and in ounces and pounds in the US. One ounce is 28.35 g and one pound is 453.59 g. Professional bakers and most modern recipe writers prefer grams, because a scale reads the same everywhere and does not care about cup size or how a liquid is poured.
A fluid ounce is a volume and an ounce is a weight. A recipe that says "8 oz milk" almost always means 8 fluid ounces, but a recipe that says "8 oz chocolate" means weight. When the unit is unclear, look at the ingredient: pourable liquids are normally fluid ounces, solids are weights.
| Liquid | Grams per US cup | Grams per 100 ml | Ounces per US cup |
|---|---|---|---|
| Water | 237 g | 100 g | 8.3 oz |
| Whole milk | 244 g | 103 g | 8.6 oz |
| Buttermilk | 245 g | 104 g | 8.6 oz |
| Heavy cream | 238 g | 101 g | 8.4 oz |
| Chicken stock | 240 g | 101 g | 8.5 oz |
| Lemon juice | 244 g | 103 g | 8.6 oz |
| White vinegar | 240 g | 101 g | 8.5 oz |
| Soy sauce | 256 g | 108 g | 9.0 oz |
| Vegetable oil | 218 g | 92 g | 7.7 oz |
| Olive oil | 216 g | 91 g | 7.6 oz |
| Maple syrup | 322 g | 136 g | 11.4 oz |
| Honey | 339 g | 143 g | 12.0 oz |
These are typical values from food-composition data. Brand, temperature and fat content move them by a few percent. The pattern is what matters: water-based liquids sit within 5 percent of water, oils are about 8 percent lighter, and syrups are 35 to 45 percent heavier.
Volume is the right choice when the amount is not critical or the liquid is thin: stock for soup, milk in a batter, water for boiling, juice in a marinade. A liquid measuring cup is quick, there is nothing to wash, and a few percent of error rarely changes the result. Use spoons for amounts under 2 tablespoons, and read the line at eye level at the bottom of the curved surface.
Weight is the better choice when accuracy matters or the liquid is thick:
"A pint's a pound the world around" is a US memory aid: 16 fluid ounces of water weighs about 1.04 pounds. The British version is "a pint of pure water weighs a pound and a quarter": 20 imperial fluid ounces of water weighs 1.25 pounds. Both are close approximations for water-like liquids and wrong for oil or honey.
Example: 1 cup of honey in a US recipe is 236.59 ml, which weighs about 339 g. In a metric-cup recipe, 1 cup of honey is 250 ml and about 358 g, so using the wrong cup adds around 19 g of honey.
For the full list of cooking liquids and how each behaves, see the top 20 liquid ingredients. For dry ingredients, see US cups to grams.