Reviewed by the CupOrGram Editorial TeamSources: King Arthur Baking, USDA FoodData CentralMethodology
The finding
The two most-cited sources for baking weights — King Arthur Baking and USDA FoodData Central — disagree about what a cup of common ingredients weighs, sometimes by as much as 14%. Neither is wrong. But a recipe that mixes them is. We compared the published values behind our 132-ingredient dataset; here's where they diverge, why, and the reconciled data as a free download.
Where the sources disagree
Our values against King Arthur's published ingredient weight chart (retrieved July 2026), sorted by the size of the disagreement. Where King Arthur lists a smaller volume, we scaled to 1 US cup and noted it.
The headline rows: cornstarch differs by 14%, rolled oats by 10%, whole milk by 7.5% — between two sources a careful baker would consider equally authoritative. Milk shows why: USDA lists milk's density at about 1.03 g/ml, which works out to 244 g per 236.59 ml cup, while King Arthur publishes a rounded practical 227 g. A lab number and a kitchen number, both defensible, 17 g apart.
Why published weights diverge
Method: measured vs derived.Kitchen charts weigh a technique (spoon-and-level, packed, sifted); density databases measure mass per volume in controlled conditions and the cup weight is arithmetic. Different questions, different answers.
Rounding conventions.Practical charts round to friendly numbers (227 g = 8 oz exactly). Derived values keep the decimals. On dense ingredients that gap alone is several percent.
Fill technique assumptions.Powdered sugar sifted or unsifted differs ~15%. Brown sugar packed or loose differs more. Sources don't always state which they assume — we note it wherever it matters, as with flour's scoop-vs-spoon problem.
The cup itself.US legal cup (240 ml), US customary (236.59 ml), metric (250 ml), Indian cups (200–250 ml). A source's cup definition moves every number in its table.
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How we reconcile them
CupOrGram's rule is consistency over allegiance: for each of the 132 ingredients we standardize on the best-supported published value — King Arthur's kitchen weights for dry baking staples, USDA-derived densities where a standardized baking source doesn't exist — and then use that single value on every page of this site. A recipe converted here never mixes sources mid-bake, which is the error that actually ruins results. Full details on the methodology page.
The dataset at a glance
One US cup (236.59 ml) holds anywhere from 60 g to 340 g depending on what's in it — a 5.7x spread across the 132 ingredients we track:
Category patterns follow density: liquids average 252 g/cup, dairy & fats average 238 g/cup, sugars & sweeteners average 228 g/cup, flours & grains average 134 g/cup, spices average 110 g/cup. The full per-ingredient table lives on the baking measurement reference.
Download the dataset
All 132 ingredients — density in g/ml and grams per US cup, one reconciled value each. CSV, free to use with attribution (a link to cuporgram.com).
Why do King Arthur and USDA disagree about what a cup weighs?
Different methods answer different questions. King Arthur publishes practical kitchen weights — what lands in a cup using their recommended technique, rounded for usability. USDA FoodData Central publishes laboratory density data, from which a cup weight is derived mathematically (density × 236.59 ml). Whole milk is the clearest example: USDA density (1.03 g/ml) works out to 244 g per cup, while King Arthur rounds to 227 g. Neither is wrong; they're measuring differently.
Which value should I use in my baking?
Either — as long as you never mix sources inside one recipe. A recipe developed against King Arthur's 120 g flour cup, converted with a 125 g assumption, drifts 4% before you preheat the oven. CupOrGram standardizes on one reconciled value per ingredient across all of our pages precisely so that can't happen here.
Can I use this dataset in my own project?
Yes — the CSV is free to download and use with attribution (a link to cuporgram.com). It covers 123 ingredients with density in g/ml and grams per US cup (236.59 ml), one reconciled value per ingredient.
Why is the spread between ingredients so large?
Density. A US cup is a fixed 236.59 ml of space, but what fills it ranges from airy dried basil (60 g) to dense molasses (340 g) — a 5.7x spread. That's the entire argument against volume measurement for anything but liquids: the cup is constant, the contents aren't.