We separate defined unit relationships from published ingredient portions. They answer different questions and carry different limits.
1. Conversions within the same measurement
Volume-to-volume calculations use each selected unit’s defined volume. Weight-to-weight calculations use each unit’s defined mass. The general operation is:
result = input × input unit factor ÷ output unit factor
Cups, fluid ounces, tablespoons, and teaspoons retain their named standards. The US customary cup and US food-label cup have separate definitions. Our source directory identifies the references used.
2. Conversions for ingredients
An ingredient record stores a published portion and its gram weight. The general operation is:
estimated grams = source portions × grams per source portion
The reverse operation divides grams by the same portion weight. When ounces by weight are requested, the result is derived from that gram amount. We do not separately substitute a source chart’s rounded ounce column.
3. When the source cup capacity is unknown
The current ingredient references do not confirm the capacity of their cup portions in milliliters. The calculator labels these as source portions and does not offer a switch to an exact US, metric, or Imperial cup for the ingredient calculation.
A proportional calculation can scale a source portion. It cannot establish a missing density. Unknown food data are not filled in with water or an average of unrelated ingredients.
4. Rounding and practical accuracy
Unit calculations retain more precision internally than may be shown in the result. Ingredient values are displayed as estimates. More decimal places would not remove variation in the food, source measurement, or measuring technique.
If a recipe gives its own gram quantity, use it. Our selected source is a stated convention for an estimate, not a claim that every recipe author uses the same one.
5. Sources and revisions
Calculator outputs identify the source record and data release. The default answers, conversion tables, and interactive calculations are generated from the same release’s calculation rules and ingredient data. A source-review date records when a reference was checked; it is not a claim that we weighed the food ourselves.
See the references for record details. If a result needs investigation, the correction-note template helps preserve the input, units, source, and expected result.
Kitchen fractions and rounding
Inputs such as 3/4, ¾ and 1 1/2 are parsed as fractions before calculation. The engine combines unit factors and input amounts as exact ratios. It rounds values for display, and marks an approximation with ≈. Ingredient estimates are also marked with ≈ because they depend on a published portion.
Record checks and corrections
The dates below record review of the cited food portions. The printable tables and the interactive calculator use the same registry. When a definition or portion changes, we rerun the related tests and record the change and date.
| Ingredient | Published portion | Source and record | Checked |
|---|---|---|---|
| All-purpose flour | 1 cup, 120 g | King Arthur Baking ingredient weight chart All-Purpose Flour | |
| Granulated white sugar | 1 cup, 198 g | King Arthur Baking ingredient weight chart Sugar (granulated white) | |
| Butter | 1/2 cup, 113 g | King Arthur Baking ingredient weight chart Butter | |
| Whole cow’s milk | 1 cup, 244 g | USDA ARS food portions, section 1.051 1.051 Whole Milk | |
| Powdered sugar | 1 cup unsifted, 120 g | USDA FoodData Central SR Legacy, FDC 169656 169656 | |
| Active dry yeast | 1 tablespoon, 12 g | USDA FoodData Central SR Legacy, FDC 175043 175043 | |
| Raw garlic | 1 cup, cut size unspecified, 136 g | USDA FoodData Central SR Legacy, FDC 169230 169230 | |
| Raw blackberries | 1 cup raw blackberries, 144 g | USDA FoodData Central SR Legacy, FDC 173946 173946 | |
| Raw blueberries | 1 cup raw blueberries, 148 g | USDA FoodData Central SR Legacy, FDC 171711 171711 | |
| Raw diced potatoes, flesh and skin | ½ cup diced, raw, flesh and skin, 75 g | USDA FoodData Central SR Legacy, FDC 170026 170026 | |
| Shredded cheddar | 1 cup shredded cheddar, 113 g | USDA FoodData Central SR Legacy, FDC 173414 173414 |
Report a measurement error with the selected units, input and result. For a food, include the exact record shown by the converter.
Unit Definitions
The registry stores separate mass, volume and temperature definitions. A defined mass converts without knowing the food. To estimate mass from a kitchen measure, select the food and the matching household portion.
US, Imperial and metric differences
US and Imperial liquid containers have separate pint, quart and gallon capacities. Their fluid ounces differ. The international avoirdupois pound and ounce use the same mass definitions in the US and UK. A troy ounce has a separate mass definition.
A US customary cup is 236.5882365 mL. The US nutrition-label equivalent is 240 mL, and a metric cup is 250 mL. A Japanese cooking cup is 200 mL, while a Japanese rice cup is 180 mL. An Australian tablespoon is 20 mL.
The oven chart converts Fahrenheit and Celsius with the temperature offset as well as the scale factor. The chart describes temperature settings. Changing a recipe’s yield does not automatically change its oven setting.
Data change log
Added household portions for seven foods and references for Imperial liquid measures and oven temperatures. These records support the expanded ingredient directory, unit converters and charts. Existing ingredient portions keep their original sources.
Sources: USDA FoodData Central, UK Weights and Measures Act and NIST unit and temperature guidance.
For a correction, we record the page, prior value, revised value, source, review date and reviewer, then rerun the relevant calculations before publishing.