Why is a US cup 236.59 milliliters and not 240?

The exact US customary cup is 236.5882365 milliliters, defined as half a US liquid pint. The 240 milliliter figure is the US legal cup used on nutrition labels, and many recipe writers round to it for simple math. The gap is about 1.4 percent, small enough that it almost never changes a result.

Does Kitchen Converts use the US cup or the metric cup?

Our calculators use the US customary cup of 236.5882365 milliliters unless a page states otherwise. The metric cup of 250 milliliters is common in Australia, so if your recipe came from there, expect about a 6 percent difference.

Are the ingredient weights exact?

No measurement in cups is exact. Ingredient weights are typical values from trusted baking references, and the real weight shifts with brand, humidity, and how you scoop. For baking, a kitchen scale removes that error. Our weight values follow King Arthur Baking and USDA FoodData Central.

Where do the safe cooking temperatures come from?

The safe internal temperatures on this site come from the USDA Safe Minimum Internal Temperature Chart. Poultry is 165 degrees Fahrenheit, ground meats are 160 degrees, and whole cuts of beef, pork, veal, and lamb are 145 degrees with a 3-minute rest. Always confirm with a thermometer.

Can I reuse the ingredient weight data?

Yes. The ingredient density data is published as an open dataset under a Creative Commons Attribution license. You can download it from the ingredient weight chart page and use it in your own projects with credit.

Kitchen conversion standards

Kitchen Converts builds every calculator on published measurement standards: US customary units defined by NIST, ingredient weights from King Arthur Baking and USDA FoodData Central, and safe cooking temperatures from the USDA. This page lists each standard and links to the source behind it.

A conversion tool is only as good as the definitions under it. Every number on this site traces back to a documented standard, not a guess, and this page collects all of them in one place. Use it to check our math, or to cite the same primary sources in your own recipes and projects.

How are volume units defined?

United States volume units have exact legal definitions set by the National Institute of Standards and Technology, known as NIST. A US cup is not a round number of milliliters, so our calculators carry the full precise value and round only the answer you see.

Two other cup sizes appear in recipes. The US legal cup, used on nutrition labels, is 240 milliliters. The metric cup, common in Australia and parts of Europe, is exactly 250 milliliters. The older UK imperial cup was about 284 milliliters. Our calculators use the US customary cup of 236.59 milliliters unless a page says otherwise.

US cup: 236.5882365 milliliters, equal to 8 US fluid ounces
US tablespoon: 14.7867647 milliliters, or 1/16 of a cup
US teaspoon: 4.92892159 milliliters, or 1/3 of a tablespoon
US fluid ounce: 29.5735296 milliliters, or 1/128 of a US gallon
US pint: 473.176473 milliliters, equal to 2 cups
US quart: 946.352946 milliliters, equal to 4 cups
US gallon: 3785.411784 milliliters, defined as 231 cubic inches

How are weight units defined?

Weight units come from the international avoirdupois system, the same definitions NIST publishes for the United States. These values are fixed by international agreement and do not change.

A weight ounce and a fluid ounce share a name but measure different things. A weight ounce measures mass. A fluid ounce measures volume. For water the two land close together, but for honey, flour, or oil they do not.

Ounce: exactly 28.349523125 grams
Pound: exactly 453.59237 grams, equal to 16 ounces
Kilogram: exactly 1000 grams, about 2.205 pounds
Gram: the base metric unit of mass used throughout the site

Where do the ingredient weights come from?

Ingredient weights, the grams in a cup of flour or sugar, are not fixed by law. They depend on the food and how it is measured. We use published values from King Arthur Baking, USDA FoodData Central, and the America's Test Kitchen ingredient chart, then cross-check them against each other.

Flour values assume the spoon-and-level method: spoon the flour into the cup and level the top with a straight edge. Scooping the cup into the bag packs the flour and adds 10 to 25 grams. Brown sugar values assume the cup is packed firm, the way most recipes expect it.

The full per-ingredient table is published on our ingredient weight chart, and the raw numbers are released as an open dataset under a Creative Commons license so anyone can check or reuse them.

What oven temperature standards are used?

Oven temperatures convert with a fixed formula. To change Fahrenheit to Celsius, subtract 32, multiply by 5, then divide by 9. The Fahrenheit scale sets water freezing at 32 degrees and boiling at 212. The Celsius scale sets the same two points at 0 and 100.

British recipes often use gas marks instead of degrees. Gas mark 4 is the baking standard, the same as 350 Fahrenheit or 177 Celsius, and the scale runs in steps of about 25 Fahrenheit. Convection and air fryer settings sit lower than standard oven settings because moving hot air transfers heat faster.

What are the safe internal cooking temperatures?

Safe internal temperatures for meat come from the United States Department of Agriculture. These are food-safety minimums, measured with a thermometer in the thickest part of the food, away from bone.

The 3-minute rest after cooking lets the temperature hold and finish the job. Cooking time charts are a starting point only. A thermometer is the real standard, because oven heat, cut thickness, and starting temperature all change the result.

Poultry, all cuts and ground: 165 degrees Fahrenheit (74 Celsius)
Ground beef, pork, lamb, and veal: 160 degrees Fahrenheit (71 Celsius)
Fresh beef, pork, veal, and lamb steaks, roasts, and chops: 145 degrees Fahrenheit (63 Celsius), then a 3-minute rest
Fish and shellfish: 145 degrees Fahrenheit (63 Celsius)
Egg dishes: 160 degrees Fahrenheit (71 Celsius)
Leftovers and casseroles: 165 degrees Fahrenheit (74 Celsius)

What other cooking standards does the site follow?

A few tools rest on standards from outside the volume and weight systems.

Baker's percentage: flour is set to 100 percent and every other ingredient is measured against it. This is the standard system for bread formulas.
Coffee brewing ratio: the Specialty Coffee Association golden ratio of about 1 part coffee to 16 through 18 parts water.
Egg sizes: set by the USDA by minimum weight per dozen. A large egg is about 50 grams without the shell.
Butter sticks: a US stick of butter is a quarter pound: 4 ounces, 113 grams, 8 tablespoons, or half a cup.

How often are these values reviewed?

Unit definitions, such as the milliliters in a cup or the grams in an ounce, are fixed and never change. Ingredient densities and food-safety temperatures can be revised by their sources, so we review those against the published references and show a review date on each tool.

When a source corrects a value, we update the calculator and the open dataset together. If you spot a number that looks wrong, the contact page is the fastest way to flag it.

Sources we rely on

These are the primary references behind the numbers on this site. Government and standards bodies come first, trusted baking references second.

NIST Office of Weights and Measures
Legal definitions of US customary volume and weight units.
NIST Handbook 44
The reference standard for US measurement units.
USDA FoodData Central
Ingredient composition and weight data.
USDA Safe Minimum Internal Temperature Chart
Safe internal cooking temperatures for meat, poultry, and eggs.
King Arthur Baking Ingredient Weight Chart
Per-ingredient baking weights.
America's Test Kitchen
Independent testing of measuring and weighing methods.
Specialty Coffee Association
Coffee brewing ratio guidance.

Frequently asked questions

Why is a US cup 236.59 milliliters and not 240?: The exact US customary cup is 236.5882365 milliliters, defined as half a US liquid pint. The 240 milliliter figure is the US legal cup used on nutrition labels, and many recipe writers round to it for simple math. The gap is about 1.4 percent, small enough that it almost never changes a result.
Does Kitchen Converts use the US cup or the metric cup?: Our calculators use the US customary cup of 236.5882365 milliliters unless a page states otherwise. The metric cup of 250 milliliters is common in Australia, so if your recipe came from there, expect about a 6 percent difference.
Are the ingredient weights exact?: No measurement in cups is exact. Ingredient weights are typical values from trusted baking references, and the real weight shifts with brand, humidity, and how you scoop. For baking, a kitchen scale removes that error. Our weight values follow King Arthur Baking and USDA FoodData Central.
Where do the safe cooking temperatures come from?: The safe internal temperatures on this site come from the USDA Safe Minimum Internal Temperature Chart. Poultry is 165 degrees Fahrenheit, ground meats are 160 degrees, and whole cuts of beef, pork, veal, and lamb are 145 degrees with a 3-minute rest. Always confirm with a thermometer.
Can I reuse the ingredient weight data?: Yes. The ingredient density data is published as an open dataset under a Creative Commons Attribution license. You can download it from the ingredient weight chart page and use it in your own projects with credit.

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