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Why One Cup of Flour Is Not One Cup of Sugar
There is no single answer to "how many grams in a cup", and every chart that gives you one is quietly wrong about something. The reason is worth two minutes, because it also explains why your bakes come out differently from the same recipe.
8 min read · updated 8 August 2026 · links to 10 tools
In short
A cup measures volume and a gram measures mass, so the conversion depends entirely on the density of what is in the cup. One US cup of water is 237 g, of granulated sugar about 200 g, and of all-purpose flour about 125 g — and that flour figure swings by up to 20% depending on how the cup was filled. Weigh flour if you can; for everything else, a per-ingredient conversion is close enough.
The reason there is no single number
A cup is a container. A gram is an amount of matter. Asking how many grams are in a cup is like asking how many kilograms are in a suitcase — it depends what you packed.
Water is the reference because it is convenient: one millilitre of water weighs one gram, near enough, so a 237 ml US cup of water is 237 g. Everything else is heavier or lighter than water by its density, and for baking ingredients the spread is large.
What a cup of each thing actually weighs
Read the flour and sugar rows together, because that pairing is where recipes go wrong most often. Swapping a cup of sugar for a cup of flour by volume changes the mass by 75 g — more than half again. Any recipe that gives both in cups and any substitution done by volume inherits that error.
Each of those has its own conversion page with the density behind it: Cups to Grams — All-Purpose Flour, Cups to Grams — Granulated Sugar, Cups to Grams — Honey and the rest. They exist separately rather than as one calculator precisely because the answer is different for each.
| One US cup of | Weighs about | Compared to water |
|---|---|---|
| Water | 237 g | — |
| Granulated sugar | 200 g | 16% lighter |
| All-purpose flour | 125 g | 47% lighter |
| Brown sugar, packed | 220 g | 7% lighter |
| Butter | 227 g | 4% lighter |
| Honey | 340 g | 43% heavier |
| Rolled oats | 90 g | 62% lighter |
| Cocoa powder | 85 g | 64% lighter |
Flour is the worst offender, and it is not close
Flour compacts. How you get it into the cup changes how much is in there by up to 20%, and that is the largest uncontrolled variable in home baking.
Dipping the cup into the bag and scraping it level — what most people do — packs the flour and gives roughly 140–150 g. Spooning flour into the cup and levelling it off without pressing gives about 120–125 g. Sifting first gives less again. That is a difference of a quarter of a cup of flour in a recipe that called for one.
This is why a cake comes out dense one week and fine the next from the same recipe, and why professional recipes are written in grams. It is not a skill problem.
The 125 g figure used across this site is spooned and levelled, which is the convention American recipe writers and King Arthur use. If a recipe was developed by dipping, its cup was heavier than yours.
If you take one thing from this: a £10 kitchen scale removes this entire problem. Weighing flour is faster than levelling a cup, needs no washing up, and is the single change that makes home baking repeatable.
And the cup itself is not one size
On top of density, "cup" means different volumes in different places.
The US customary cup is 236.6 ml. The US legal cup, used on nutrition labels, is 240 ml. The metric cup used in Australia and New Zealand is 250 ml. The old imperial cup was 284 ml. A recipe from an Australian blog using metric cups gives you 6% more of everything than the same numbers read as US cups — enough to matter in baking, not enough to be obvious.
The US cup to Millilitre Converter and Metric cup to Millilitre Converter converters cover the volumes themselves; the ingredient pages above handle volume and density together.
When it matters and when it does not
Baking is chemistry. The ratio of flour to fat to sugar to liquid decides the structure, and a 20% error in flour changes the result. Weigh it.
Cooking is not. A stew with 20% more onion is a stew. Volume measures are fine, and the precision is not worth the washing up.
The dividing line is roughly whether the recipe rises. Anything with a raising agent, a dough or a batter deserves a scale. Anything you can taste and adjust does not.
For scaling a recipe up or down, Recipe Scaler rescales quantities and returns halves and thirds rather than 0.667 of a cup — and deliberately refuses to guess at the new cooking time, because that does not scale linearly and pretending otherwise ruins things.
Frequently asked questions
How many grams is one cup?
It depends entirely on what is in the cup, because a cup is a volume and a gram is a mass. One US cup is 237 g of water, about 200 g of granulated sugar, about 125 g of all-purpose flour and about 340 g of honey. Any chart offering a single number for "a cup" is giving you water and hoping.
Why do my bakes come out differently each time from the same recipe?
Most often it is how the flour was measured. Dipping the cup into the bag packs it and can give 20% more flour than spooning and levelling — a quarter of a cup extra in a one-cup recipe. Weighing removes the variable entirely, which is why professional recipes are written in grams.
Is an Australian cup the same as an American one?
No. The metric cup used in Australia and New Zealand is 250 ml against the US customary 236.6 ml, so an Australian recipe gives you about 6% more of everything if you read its cups as American. Enough to matter in baking, not enough to notice until the result is wrong.
Should I sift flour before or after measuring?
It changes the answer, so follow the recipe's wording exactly. "One cup sifted flour" means sift first, then measure — that is less flour. "One cup flour, sifted" means measure first, then sift — that is more. The two are not the same amount, which is why weighing sidesteps the argument.