How the conversion works
Volume measurements like cups, tablespoons and teaspoons are first converted to millilitres, while weight measurements are handled in grams. Within the same type, conversion is straightforward.
Crossing between volume and weight needs the ingredient density, expressed in grams per millilitre. That is why the same cup measure gives a different gram weight for flour than for water.
Why the ingredient matters
A cup is a measure of space, but a gram is a measure of mass. Light, fluffy ingredients fill more space per gram than dense ones, so density is the bridge between the two.
- Water sits at roughly one gram per millilitre, the simplest case.
- Flour is much lighter by volume, so a cup weighs far less than a cup of water.
- Sugar and butter fall in between, each with its own density.
Practical tips
Baking rewards precision, so converting volume recipes to weight often gives more consistent results batch to batch.
- Weigh ingredients when a recipe is fussy about ratios, like bread or pastry.
- Spoon and level flour rather than scooping to match typical density assumptions.
- For liquids, volume and weight are close but not identical except for water.
Caveats and common mistakes
The densities used here are approximate. Real values shift with brand, humidity, sifting and how firmly an ingredient is packed, so treat conversions as a close guide rather than an exact figure.
Picking the wrong ingredient is the most common error in volume-to-weight conversions, since it silently changes the density applied.
Formula
volume↔ml, weight↔g, grams = ml × densityFrequently asked questions
- Why does the ingredient matter?
- Converting between volume and weight depends on density. A cup of flour and a cup of sugar weigh different amounts, so the ingredient sets the density used.