Water: why 227 g per cup is wrong
King Arthur Baking Ingredient Weight Chart publishes 227 g (8 oz) per US cup of water. This site rejects that figure and publishes 236 g (8.3 oz) instead, from CRC Handbook of Chemistry and Physics, 84th edition: density of water (density 0.9982 g/mL, matching the composition of the substance). The reason:
Water at room temperature is 0.998 g/mL (CRC Handbook), so a US cup of 236.6 mL weighs 236 g. 227 g is 8 weight ounces: a cup of 8 fluid ounces read as 8 weight ounces, although a fluid ounce of water weighs 29.6 g, not 28.35 g. Water only comes down to 227 g per cup near boiling (0.958 g/mL at 100 °C), not at any temperature a recipe measures it.
The arithmetic
| Source | 1 cup | Density | Status |
|---|---|---|---|
| King Arthur Baking Ingredient Weight Chart | 227 g8 oz | 0.9595 g/mL | Rejected on physics |
| CRC Handbook of Chemistry and Physics, 84th edition: density of water | 236 g8.3 oz | 0.9982 g/mL | Published here |
The 227-gram pattern
The figure 227 is 8 × 28.35 — the conversion for weight ounces (avoirdupois). It is applied to volume in fluid ounces without going through the substance’s density. For a substance that happens to have a density of about 0.96 g/mL, the answer would be right; for water, milk, yogurt, cream, buttermilk, pumpkin purée, ricotta and evaporated milk, all of which are denser than water, it is wrong. The same number 227 appears on the King Arthur chart for every one of these ingredients, which is the signature of an arithmetic pattern rather than a measurement.
The full list of 227-gram rejections is on the corrections page.
The published figure and its sources
The full sourcing for water, including every accepted and rejected figure, the state or filling method behind each, and the physics or standards reasoning applied, is on the ingredient page.
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