Cups, grams, millilitres: what actually converts
Volume converts to volume exactly: 1 US cup is 236.588 mL, so 2 cups is 473.2 mL, and a tablespoon is always three teaspoons. Weight converts to weight exactly too: an ounce is 28.35 g and a pound 453.6 g. The awkward step is between the two, because a cup measures space and a gram measures mass — the bridge is density, and density is different for every ingredient. A cup of water weighs 237 g; a cup of all-purpose flour weighs about 125 g; a cup of honey weighs 340 g.
The cup is not an international unit
| Cup | Volume | 1 cup of flour | Used in |
|---|---|---|---|
| US cup | 236.588 mL | ≈ 125 g | US recipes, most English-language baking sites |
| Metric cup | 250 mL | ≈ 132 g | Australia, New Zealand, Canada |
| UK / imperial cup | 284.131 mL | ≈ 150 g | Older British recipes |
| Japanese cup (カップ) | 200 mL | ≈ 106 g | Japanese recipes, rice cookers |
If a recipe says "1 cup (250 ml)" it has told you it means a metric cup. If it just says "1 cup" and was written for a US audience, use 236.588 mL. When the difference matters — cakes, bread, anything where a 20% flour swing changes the structure — weigh in grams and sidestep the question entirely.
Tablespoons are worse
A US tablespoon is 14.79 mL, a UK tablespoon 17.76 mL and an Australian tablespoon 20 mL. In small quantities this rarely ruins anything, but a recipe using 4 tablespoons of an Australian tablespoon is 80 mL against 59 mL in the US — a third more liquid. Teaspoons are more consistent at about 4.93 mL (US) and 5.92 mL (UK).
Ounces come in two kinds
Fluid ounces measure volume and ounces measure weight. Water is the only common ingredient where they nearly coincide (1 fl oz ≈ 29.6 mL ≈ 29.6 g), which is exactly why the confusion survives. A fluid ounce of oil weighs about 27 g, of honey about 42 g, of flour about 15 g. When a recipe says "8 oz of chocolate" it means weight; "8 fl oz of milk" means volume.
Common densities (grams per US cup)
| Ingredient | g per cup | Ingredient | g per cup |
|---|---|---|---|
| Water | 237 | Granulated sugar | 200 |
| All-purpose flour | 125 | Brown sugar (packed) | 213 |
| Bread flour | 127 | Butter | 227 |
| Cocoa powder | 85 | Honey | 340 |
| Rolled oats | 90 | Rice, uncooked | 185 |
| Milk | 244 | Vegetable oil | 216 |
Two habits make cup measuring more reliable if you must use it: spoon the flour into the cup and level it with a knife instead of scooping from the bag, and pack brown sugar firmly before levelling. Both are worth 10–20% of the final weight, which is exactly the margin that decides whether a batch of cookies spreads or stays put.
Frequently asked questions
How many grams is 1 cup?
It depends entirely on the ingredient: 237 g for water, 125 g for all-purpose flour, 200 g for granulated sugar, 227 g for butter and 340 g for honey. Volume and weight only connect through density, which is why a single "cups to grams" number cannot exist.
Is a US cup the same as a metric cup?
No. A US cup is 236.588 mL and a metric cup — used in Australia, New Zealand and Canada — is 250 mL, 5.6% larger. A UK/imperial cup is 284.131 mL, 20% larger than the US one. If a recipe writes "1 cup (250 ml)" it means the metric cup.
How many tablespoons in a cup?
Sixteen US tablespoons, or 48 US teaspoons, in one US cup. In Australia a tablespoon is 20 mL rather than 14.79 mL, so an Australian cup holds only 12½ tablespoons — one more reason to convert to millilitres when a recipe crosses borders.
What is the difference between an ounce and a fluid ounce?
An ounce measures weight (28.35 g) and a fluid ounce measures volume (29.57 mL). They coincide only for water. A fluid ounce of honey weighs about 42 g and a fluid ounce of flour about 15 g, so never swap them in a recipe.
Why does my recipe say 240 ml for a cup?
Nutrition labelling rounds the US cup to 240 mL for convenience. The legal definition is 236.588 mL, a difference of under 1.5%, which is too small to matter in practice but explains where the 240 figure comes from.
How do I convert millilitres to grams?
Multiply the millilitres by the density in grams per millilitre, which is the grams-per-cup figure divided by 236.588. Water is 1 g/mL, so 100 mL is 100 g; flour is about 0.53 g/mL, so 100 mL of flour is roughly 53 g.
Should I weigh or use cups?
Weigh whenever you can. Cup measurement of flour varies by 10–20% depending on whether it was sifted, spooned or scooped, which is enough to change a cake from light to dense. A basic kitchen scale removes the variable permanently.
What about Australian tablespoons and Japanese cups?
An Australian tablespoon is 20 mL and a Japanese cup (カップ) is 200 mL, while Japanese rice cookers use their own 180 mL cup. Both are large enough differences to matter, so convert to millilitres or grams when you cook from a recipe written in another country.