The measures a US kitchen runs on
The US volume system is built on the fluid ounce and doubles cleanly from there, which is why the numbers are worth memorising rather than looking up.
| Unit | In fluid ounces | In millilitres |
|---|---|---|
| Teaspoon | 1/6 | 4.93 |
| Tablespoon (3 tsp) | 1/2 | 14.79 |
| Fluid ounce (2 tbsp) | 1 | 29.57 |
| Cup | 8 | 236.59 |
| Pint | 16 | 473.18 |
| Quart | 32 | 946.35 |
| Gallon | 128 | 3,785.41 |
Two cups to a pint, two pints to a quart, four quarts to a gallon. The gallon figure is exact by definition — a US gallon is 231 cubic inches, and every other unit above is a fixed fraction of it.
The three mismatches that break recipes
A cup, a pint and a fluid ounce all exist in more than one system, and the words are identical.
| Measure | US | Metric or imperial | Difference |
|---|---|---|---|
| Cup | 236.6 mL | 250 mL (metric, AU/NZ) | Metric is 5.7% larger |
| Pint | 473.2 mL (16 fl oz) | 568.3 mL (imperial, 20 fl oz) | Imperial is 20% larger |
| Fluid ounce | 29.57 mL | 28.41 mL (imperial) | US is 4% larger |
The pint is the dangerous one. A British recipe calling for a pint of milk wants nearly a fifth more than a US pint, which is enough to change a custard from set to soup. The fluid ounce runs the other way, and is small enough that it rarely matters on its own — but an imperial pint being 20 of the smaller ounces against the US pint's 16 of the larger ones is exactly how a 20% error hides behind two units that both look right.
Australian recipes add one more: their tablespoon is 20 mL, four teaspoons rather than three. Four Australian tablespoons of baking powder is five US ones, which is the difference between a rise and a soapy aftertaste.
Units that have no standard at all
Some things people measure with are not measures. A spoon out of the flatware drawer is designed to look right beside a plate; depending on the pattern it holds anywhere from about 11 to 15 mL, and how level you hold it moves that further. A coffee scoop is usually sold as two tablespoons but the ones packed in with grinders are often a tablespoon and a half.
Rather than print an average and let it look authoritative, this tool shows those units as a range and says why. If the range is too wide for what you are doing — and for baking, coffee or anything with leavening it usually is — that is the answer: use a real measuring spoon, or better, a scale.
Volume is the wrong tool for dry ingredients
Everything above concerns liquids, where a cup is a cup. For dry goods, volume measures how much air is in there along with the flour. A cup of all-purpose flour is anywhere from about 120 g spooned and levelled to 145 g or more scooped straight out of the bag and tapped down — a swing of 20% that no conversion table can rescue, because the variation is in your hand rather than in the units.
This is why professional and European recipes give grams for dry ingredients and why serious baking books have converted. If a recipe offers both, take the weights. If it only offers cups and the result matters, weigh one cup of your flour the way you normally fill it, write the number inside the cover of the book, and use that from then on. Your own consistent figure beats a published average, because it accounts for how you actually scoop.
Questions people ask
Is a US cup 240 mL or 236.6 mL?
Both figures are in circulation and they mean different things. The customary US cup used in recipes is 8 US fluid ounces, which is 236.588 mL. The 240 mL figure is the "legal" or "nutrition labeling" cup defined by the FDA for food labels, rounded for convenience. The 1.4% gap is irrelevant for a cup of stock and starts to matter when you are scaling a recipe by eight. This tool uses 236.588 mL, the customary cup, because that is what a recipe means.
How many ounces are in a gallon?
128 US fluid ounces, exactly: four quarts, eight pints, sixteen cups. An imperial gallon is 160 imperial fluid ounces, which works out to 4.546 L against the US gallon's 3.785 L — about 20% larger, the same proportion as the pint difference, since both systems have the same number of pints to the gallon.
Can I convert a cup of flour to grams here?
Not directly, and no tool honestly can with one number. The volume-to-weight ratio depends on the ingredient and, for anything powdery, on how it was put in the cup. This converter handles volume against volume and weight against weight, which are fixed relationships. For flour, the common working figure is about 120 g per cup spooned and levelled, but treat that as a starting point and weigh your own if the recipe is fussy.
Why does the oven table pair 350 °F with 180 °C when that is not the exact conversion?
Because oven dials are marked in round numbers and always have been. 350 °F is 176.7 °C, and no oven made has a 177 setting; the metric equivalent of that dial position is 180 and has been for as long as both scales have been printed on cookware. The gas mark column is the same idea from British ovens. Use the row, not the arithmetic — and calibrate against a thermometer, because your oven is probably further off than the rounding is.