Following a recipe from another country often means facing cups when you have a kitchen scale, or grams when you have measuring cups. Learning the cooking conversions between cups, grams, and millilitres makes any recipe usable, and clears up the single most confusing point: cups to millilitres is fixed, but cups to grams depends entirely on the ingredient. This guide gives you the reliable conversions, a table of common baking ingredients, and the reason a cup of flour and a cup of sugar weigh completely different amounts. It is the companion you want when a recipe and your tools do not match. For any measurement swap, our unit converter handles it instantly.
Quick answer: One US cup equals about 240 ml (a metric cup is 250 ml). But cups to grams depends on the ingredient: 1 cup of water is about 240 g, plain flour about 120 g, and granulated sugar about 200 g, because each has a different density.
Cups to millilitres (the easy one)
Millilitres measure volume, and so do cups, so this conversion is fixed regardless of the ingredient.
1 US cup = 240 ml (236.6 ml precisely)
1 metric cup = 250 ml
So a cup of water, milk, or oil is always about 240 ml in a US recipe. Note the small difference between the US cup and the metric cup used in some countries; for most cooking it does not matter, but for baking it can.
Cups to grams (the tricky one)
Grams measure weight, not volume, so converting cups to grams depends on how heavy the ingredient is, its density. A cup is a fixed space, but that space holds a different weight of flour than of sugar or butter.
This is why you cannot use a single cups-to-grams number. A cup of light, airy flour weighs far less than a cup of dense sugar, even though both fill the same cup.
Common ingredient conversions
Here are approximate weights for one US cup of common baking ingredients:
| Ingredient (1 US cup) | Approx. weight |
|---|---|
| Water | 240 g |
| Plain (all-purpose) flour | 120 to 125 g |
| Granulated sugar | 200 g |
| Brown sugar (packed) | 220 g |
| Butter | 227 g |
| Rolled oats | 90 g |
| Rice (uncooked) | 185 g |
These are typical values; brands and how you pack or sift an ingredient cause small variations, especially with flour.
Convert and scale
Our unit converter switches between cups, grams, and millilitres, and our recipe scaler calculator resizes a recipe for a different number of servings.
Why weight beats volume
Serious bakers prefer weighing ingredients in grams over measuring in cups, and for good reason. Weight is exact, while a cup of flour can vary by 20% or more depending on whether it is scooped, spooned, or sifted. That variation can be the difference between a light cake and a dense one.
If a recipe gives weights, use a kitchen scale for the most reliable results. If it only gives cups, the table above lets you convert to grams and weigh instead.
Frequently asked questions
How many grams are in a cup?
It depends on the ingredient, because grams measure weight and a cup measures volume. One US cup of water is about 240 grams, plain flour is around 120 to 125 grams, granulated sugar is about 200 grams, and butter is about 227 grams. Each ingredient has a different density, so there is no single cups-to-grams number.
How many millilitres are in a cup?
One US cup is about 240 millilitres (236.6 precisely), while a metric cup used in some countries is 250 millilitres. Because both cups and millilitres measure volume, this conversion is fixed and does not depend on the ingredient. So a cup of any liquid, water, milk, or oil, is about 240 ml in a US recipe.
Why is a cup of flour different in grams from a cup of sugar?
Because they have different densities. A cup is a fixed volume, but flour is light and airy while sugar is dense and heavy, so the same cup holds far more weight of sugar. A cup of flour is about 120 grams, while a cup of granulated sugar is about 200 grams, even though both fill the same space.
Is a US cup the same as a metric cup?
No, they differ slightly. A US cup is about 240 millilitres, while a metric cup is 250 millilitres. The 10 millilitre difference rarely matters for general cooking, but in baking, where ratios are precise, it can affect results. Check which cup a recipe uses, and weighing in grams avoids the issue entirely.
Should I measure ingredients by weight or volume?
Weight, in grams, is more accurate and is preferred for baking, where precision matters. A cup of flour can vary by 20% or more depending on how it is filled, while a gram is always a gram. If a recipe provides weights, use a kitchen scale. If it only gives cups, convert to grams using a conversion table.
The bottom line
Cups to millilitres is fixed, one US cup is about 240 ml, but cups to grams depends on the ingredient: a cup of flour is about 120 g, sugar about 200 g, and butter about 227 g, because each has a different density. For accuracy, especially in baking, weigh ingredients in grams rather than measuring by cup. Convert any measurement with our unit converter.
Further reading
For authoritative background on this topic, see Cup (unit) on Wikipedia.
Note. This article is for general informational purposes. Ingredient weights are approximate and vary by brand and measuring method.
Last reviewed: July 2026