Two questions before a cup becomes a weight
Almost every converter online answers neither of them. The first is whose cup, because there are three in common use. The second is what is in it, because a cup of honey weighs four times what a cup of desiccated coconut does.
Get either one wrong and the number is decorative. Get both wrong and you are further from the right answer than if you had guessed.
Whose cup
The American customary cup is 236.588 ml, being eight US fluid ounces. The metric cup used in Britain, Australia, New Zealand and Canada is a round 250 ml. Then America has a second one: the legal cup of exactly 240 ml, defined for nutrition labelling in 21 CFR 101.9, which is the cup behind the serving size on a packet.
Between the customary and the metric cup is 5.7 percent. That vanishes into a chilli and it is the difference between a sponge that rises and one that sits there. Nobody writes the difference down because within any one country there is no difference to write down, and a recipe crossing a border carries no note saying which kitchen it came from.
The market switch at the top of this page asks about the RECIPE, not about you. A British cook working from an American food blog wants the American setting, then gets grams, and the grams are the same everywhere.
Spooned and levelled, or the figure is fiction
This is the part that explains why three websites give three answers for a cup of flour and all of them are honest. A cup of flour spooned in loosely and levelled off with a knife weighs around 120 g. The same cup pushed through the bag like a scoop comes out closer to 150. That is an extra quarter of the flour, from the same cup, in the same kitchen, in the same minute.
So a density is meaningless without the method that produced it. Every figure on this page is spooned and levelled, which is the method the published chart used, and it is printed under every result rather than buried in an about page. If you scoop, you will be over, and knowing that is more useful than a number pretending to a precision the measurement does not have.
A spoon is not a small cup
Salt, baking powder, bicarbonate of soda and the whole spice rack are measured in spoons and published in spoons, so this tool uses the spoon figure rather than dividing a cup weight by forty-eight. For most of them there is no cup weight to divide. Ground cinnamon has a published teaspoon, 2.6 g, and no published cup at all, because nobody has ever needed one.
Pick a spice here and the cup option disappears from the unit list. That is the tool declining to invent a figure, and it is the behaviour to look for in any converter: one that cheerfully offers you a cup of ground cumin has told you something about itself.
The Australian tablespoon holds four teaspoons
Twenty millilitres, against fifteen everywhere else. Australia went metric in the 1970s and rounded its tablespoon up; nowhere else did. The teaspoon stayed at five, so an Australian tablespoon holds four of them and a British one holds three.
This is a bigger error than the cup and it gets far less attention. At three tablespoons of soy sauce, an Australian following a British recipe is a third over on the salt, and nothing in the recipe warns them. The four-market table under every result exists to make that visible: switch the unit to tablespoons and the spread across the four countries jumps from six percent to thirty-five.
The ingredients this page will not pretend about
Grated cheese depends on the grater. Dried pasta depends on the shape, and penne and fusilli are not the same cupful. Raw spinach collapses to a tenth of its volume the moment it meets heat, so a cup of it describes the bag rather than the dinner. Those are flagged on the result, and the flag says weigh it.
Eggs, onions, carrots and chicken breasts are not in the converter at all, because they are counted rather than measured and a cup of them means nothing. Their notes carry the useful figure instead: a medium onion is about 150 g peeled, a clove of garlic is about 3 g, a lemon gives roughly three tablespoons of juice.
Buy the scales
Everything above is a workaround for a problem that five pounds solves permanently. A gram is a gram in every country, in every measuring set, however you scooped it, which is why professional recipes are written in weight and why American baking books have started printing grams next to their cups.
Use this page for the recipe in front of you tonight. If you bake more than a few times a year, a set of digital scales removes the entire class of problem, and the tare button means one bowl instead of six cups to wash up.
Common questions
How many grams is a cup of flour?
It depends whose cup, and the honest answer is between 120 and 127 grams of plain flour. An American cup is 236.588 ml and holds 120 g. A British, Australian or Canadian cup is 250 ml and holds about 127 g. Both are right, they are just different cups, and a recipe rarely says which one it was written in. The clue is usually the rest of the recipe: if it also gives temperatures in Fahrenheit and calls the flour all-purpose, it means the American one.
Why is a US cup smaller than a UK cup?
Because they were defined from different starting points. The US customary cup is eight US fluid ounces, which works out at 236.588 ml. The metric cup used in Britain, Australia, New Zealand and Canada was set at a round 250 ml when those countries went metric, precisely so it would be an easy number. Nobody harmonised them afterwards. The gap is 5.7 percent, which disappears into a casserole and shows up in a sponge.
What is the difference between a US cup and a US legal cup?
America has two. The customary cup of 236.588 ml is the one in a measuring set on a kitchen shelf. The legal cup is exactly 240 ml and is defined in 21 CFR 101.9(b)(5)(viii) for nutrition labelling, so it is the cup behind a serving size on a packet. Recipe writers use both without saying which, and the 3.4 ml between them is not worth worrying about in a stew. This tool defaults to customary, because that is what people are actually holding, and prints the legal figure underneath when you ask for cups.
Why do different websites give different weights for a cup of flour?
Mostly because they measured it differently, not because one of them is wrong. A cup of flour spooned in loosely and levelled off weighs about 120 g. The same cup dragged through the bag and heaped comes out nearer 150. That is a quarter more flour, from the same cup, and it is the single biggest source of disagreement between charts. Every figure here is spooned and levelled, which is the method King Arthur Baking published theirs under, and the page says so because a density without a method is a number somebody made up.
Why is an Australian tablespoon different?
It is 20 ml and holds four teaspoons. Everywhere else it is 15 ml and holds three. Australia standardised on 20 ml when it went metric in the 1970s and nowhere else followed, so it is a genuine one-country measure rather than a rounding difference. It matters more than the cup does: at three tablespoons of anything strong, an Australian following a British recipe is a third over, and nothing about the recipe warns them. This is the error the market switch on this page exists to catch.
Can I convert a teaspoon of cinnamon to grams?
Yes, and it is 2.6 g, but notice what the tool will not let you do next: there is no cup figure for ground cinnamon, so it will not offer you one. That is deliberate. Nobody measures a cup of cinnamon, so no reputable chart publishes a weight for one, and a converter that produces a number anyway has multiplied a teaspoon by 48 and called it research. Ground spices, salt and raising agents have published per-spoon figures instead, because a spoon is how they are actually used.
Why does the tool refuse to convert grated cheese or pasta?
It converts them and then tells you not to trust it, which is a different thing. A cup of grated cheddar depends entirely on the grater: fine shreds pack, coarse ones bridge. A cup of pasta depends on whether it is penne or fusilli. A cup of raw spinach is meaningless because it collapses to a tenth of its volume in the pan. Those are flagged because volume measurement of them is unreliable rather than merely imprecise, and the difference is worth naming instead of hiding behind three significant figures.
Is it better to weigh ingredients than to use cups?
For baking, yes, and this is the rare kitchen question with a clean answer. A gram is a gram in every country, in every measuring set, however you scooped it. That is why professional recipes are written in grams, why British baking books moved to them decades ago, and why American baking books have started printing them alongside cups. Cups are faster for a stew and fine for it. For anything where the ratio of flour to fat to sugar decides whether it works, a five pound set of scales removes the entire problem this page exists to solve.
What is a stick of butter in grams?
One hundred and thirteen grams, which is half a US cup, eight tablespoons or four ounces. It is an American unit and it does not exist anywhere else, which is why a British reader hits it and stalls. A British 250 g block is a little over a cup, so two sticks and one block are not the same thing. Butter is one of the few ingredients where the conversion is exact rather than a density, because it is sold in a solid measured block.
Where do these ingredient weights come from?
King Arthur Baking’s Ingredient Weight Chart, which is the most widely used free reference and publishes for the US customary cup, spooned and levelled. Where a British ingredient is not on it the figure is the common published value and the ingredient note says so. We cite the miller rather than a government nutrition database on purpose: those disagree, USDA lists all-purpose flour at 125 g to the cup where King Arthur lists 120, and quoting one source’s number under another source’s name is exactly the failure this site tries not to commit.