How we calculate our conversions
Every gram figure on Grams Per Cup is a considered choice, not a random number. Here's exactly how we arrive at them — and why a cup of one ingredient can weigh so differently from a cup of another.
The cup we use
All conversions are based on the US customary cup of 236.6 ml (more precisely 236.588 ml), the cup used in the vast majority of American recipes. This is different from two other cups you may meet: the metric cup of 250 ml used in Australia and parts of Europe, and the US "legal" cup of 240 ml used on nutrition labels. Using the wrong cup across a whole recipe compounds the error, which is one more reason weighing in grams is the safest way to follow a recipe from another country.
How each ingredient is measured
A gram-per-cup figure only means something if everyone fills the cup the same way. Our values assume standard kitchen practice for each ingredient type:
- Flours and powders — spooned into the cup and levelled, never scooped or packed. Scooping straight from the bag can add 20–30 g per cup.
- Brown sugar — firmly packed, the standard recipe assumption.
- Granulated and caster sugar — poured and levelled; these don't compress meaningfully.
- Liquids — measured to the line in a liquid measuring cup.
- Grated or shredded ingredients — loosely filled, not pressed down.
Why our numbers can differ from another site
Density genuinely varies by brand, grind, moisture and packing, so reputable sources disagree — and that's normal. All-purpose flour is the clearest example:
- We use 125 g per cup.
- King Arthur Baking lists 120 g.
- America's Test Kitchen uses 142 g (a firmer fill).
We pick a well-supported mid-range value and state our measuring assumption, rather than pretending a single exact number exists. Where an ingredient is especially sensitive to how it's measured, the ingredient's own page explains it.
Rounding
We round to the nearest whole gram for amounts of 10 g and up, and to one decimal place below that. Ounces are derived from grams at 28.35 g per ounce. These are cooking figures; the small rounding involved is far below the variation you'd get from measuring by cup in the first place.
Sources
Our density figures are checked against established reference data, including:
- USDA FoodData Central — the US Department of Agriculture's food composition database.
- King Arthur Baking — Ingredient Weight Chart.
- NIST Office of Weights and Measures — for the definition of US customary units.
Reviews and corrections
Ingredient values are reviewed periodically against the sources above and when readers flag a discrepancy. If a number looks off for a brand or product you use, please tell us on the contact page — corrections are welcome and help everyone.