The two separate problems
People treat "cups to grams" as one conversion. It is two, and they fail independently.
The first is that the unit itself is ambiguous. A US cup is 236.588 mL, defined as eight US fluid ounces. An Australian cup is 250 mL. An old British cup is 284.131 mL, being ten imperial fluid ounces. The US fluid ounce is 29.574 mL and the imperial one is 28.413 mL, so they are close enough to look interchangeable and are not. Pints are where it gets expensive: a US pint is 473 mL and an imperial pint is 568 mL, a 20% gap, and the words on the page are identical.
The second is that volume tells you nothing about weight until you know what is in the cup. One US cup holds 236.6 g of water, about 200 g of granulated sugar, about 340 g of honey, and somewhere between 120 g and 145 g of all-purpose flour depending on how it got in there. There is no universal cups-to-grams number, which is why this tool asks what you are measuring.
The density table
| Ingredient | g/mL | 1 US cup | 1 tbsp | 1 tsp |
|---|---|---|---|---|
| Water, stock | 1.000 | 237 g | 14.8 g | 4.9 g |
| Whole milk | 1.031 | 244 g | 15.2 g | 5.1 g |
| Vegetable oil | 0.921 | 218 g | 13.6 g | 4.5 g |
| Butter, melted | 0.959 | 227 g | 14.2 g | 4.7 g |
| Honey | 1.437 | 340 g | 21.2 g | 7.1 g |
| Flour, AP, spooned and leveled | 0.507 | 120 g | 7.5 g | 2.5 g |
| Flour, AP, scooped from the bag | 0.613 | 145 g | 9.1 g | 3.0 g |
| Sugar, granulated | 0.845 | 200 g | 12.5 g | 4.2 g |
| Sugar, brown, packed | 0.900 | 213 g | 13.3 g | 4.4 g |
| Sugar, powdered, unsifted | 0.478 | 113 g | 7.1 g | 2.4 g |
| Cocoa powder | 0.359 | 85 g | 5.3 g | 1.8 g |
| Salt, table | 1.217 | 288 g | 18.0 g | 6.0 g |
| Salt, Morton kosher | 0.974 | 230 g | 14.4 g | 4.8 g |
| Salt, Diamond Crystal kosher | 0.568 | 134 g | 8.4 g | 2.8 g |
| Rolled oats | 0.380 | 90 g | 5.6 g | 1.9 g |
| Rice, long grain, raw | 0.782 | 185 g | 11.6 g | 3.9 g |
| Ground coffee | 0.359 | 85 g | 5.3 g | 1.8 g |
These are the working figures used across recipe development, not laboratory measurements. Liquids are reliable to a percent or two because a liquid fills a container the same way every time. Powders are not: the number depends on how the ingredient was put in the cup, how humid the kitchen is, and how long the bag has been sitting compacting itself. Treat the powder rows as good to about 10%.
Why flour breaks recipes and stock does not
The tolerance of a dish is what decides whether any of this matters. A stew that is 10% off on the stock is a stew. A cake that is 20% heavy on flour is a different cake — dry, tight, and it will not be obvious why. Bread is worse still, because hydration is calculated against flour weight, so an error in the flour propagates into the water calculation and you get a dough that behaves nothing like the one in the recipe.
That 20% is not hypothetical. Spooning flour into a cup and leveling it off gives about 120 g. Scooping the cup through the bag compacts it to about 145 g. Both are "one cup". This is the single most common reason a baking recipe fails for one person and works for another, and it is why serious recipes now print grams alongside the cups.
Where a scale stops being optional
A digital kitchen scale reading to 1 g costs about the same as two bags of good flour and removes the entire problem: no density table, no spoon-and-level technique, no ambiguity about whose cup the author meant. Set the bowl on it, zero it, add flour to the number. For anything below about 10 g — yeast, baking soda, salt in a small dough — you want a scale that reads to 0.1 g, because a 1 g scale rounding 3 g of yeast to 3 is fine but rounding 0.6 g to 1 is not.
Everything above is a way of coping when the recipe only gives volumes and you have no way to ask the author what they meant. It is a good enough coping mechanism. It is not as good as weighing.
Questions people ask
How many grams is one cup of flour?
Between 120 g and 145 g, and which one depends entirely on how you fill the cup. Spooned in and leveled off, all-purpose flour runs about 120 g per US cup. Dipped straight into the bag and scraped level, it compacts to about 145 g. Sifted first and spooned, it can drop to 105 g. Most modern American recipes assume the spoon-and-level 120 g figure, King Arthur being the widely followed reference, but plenty of older recipes were developed by scooping. If a recipe gives grams, use the grams. If it only gives cups and the result matters, spoon and level, and expect to adjust.
Is a US cup the same as a metric cup?
No. A US cup is 236.588 mL and a metric cup is 250 mL, so the metric cup is about 5.7% larger. Australian and New Zealand recipes use the 250 mL cup, and so do most European conversions of American recipes. An old British cup is 284.131 mL, being ten imperial fluid ounces, which is 20% larger than a US cup. On a single cup of milk none of this will ruin dinner. On four cups of flour in a bread it will, and on the liquid in a custard it will.
Is a fluid ounce the same as an ounce?
Only for water, and only approximately. A fluid ounce is a volume — 29.574 mL in the US system — and an ounce is a weight, 28.35 g. They happen to nearly coincide for water because water is about 1 g/mL, which is exactly why the two got the same name and why the confusion persists. Eight fluid ounces of honey weigh about 11.5 ounces. Eight fluid ounces of flour weigh about 4.2 ounces. When a recipe says "8 oz cream cheese" it means weight; when it says "8 fl oz milk" it means volume; when it says "8 oz milk" you have to guess, and the guess is usually volume.
Why does the kosher salt brand matter?
Because the crystals are shaped differently and a teaspoon of large flat crystals holds far less salt than a teaspoon of small dense ones. Diamond Crystal is about 2.8 g per teaspoon, Morton kosher about 4.8 g, and ordinary fine table salt about 6 g. That is a range of more than two to one, using the same spoon and the same word. American recipe writers overwhelmingly develop with Diamond Crystal, so a recipe calling for a tablespoon of kosher salt made with Morton delivers roughly 70% more salt than intended. If you cook from a lot of American recipes, either buy the brand they used or convert by weight.
What about a stick of butter?
One US stick is 1/2 cup, 4 ounces, 113 g, and it is one of the few volume measures in American cooking that is genuinely reliable, because the wrapper is printed with tablespoon marks and the density of butter does not vary. Four sticks make a pound. A European 250 g block is a little over two sticks, and a UK 250 g pack the same. If a recipe says "1 cup butter" that is two sticks, 227 g.