In the United States, the customary cup is half of a US liquid pint.

The cup currently used in the United States for nutrition labelling is defined in United States law as 240 ml.^[1][2][3]

The following information is describing that how to measure US legal cup in different ways.^[4]

A "cup" of coffee in the US is usually 4 fluid ounces (118 ml), brewed using 5 fluid ounces (148 ml) of water. Coffee carafes used with drip coffee makers, e.g. Black and Decker models, have markings for both water and brewed coffee as the carafe is also used for measuring water prior to brewing.^[5] A 12-cup carafe, for example, has markings for 4, 6, 8, 10, and 12 cups of water or coffee, which correspond to 20, 30, 40, 50, and 60 US fluid ounces (0.59, 0.89, 1.18, 1.48, and 1.77 litres) of water or 16, 24, 32, 40, and 48 US fluid ounces (0.47, 0.71, 0.95, 1.18, and 1.42 litres) of brewed coffee respectively, the difference being the volume absorbed by the coffee grounds and lost to evaporation during brewing.

Australia, Canada, New Zealand, and some other members of the Commonwealth of Nations, being former British colonies that have since metricated, employ a "metric cup" of 250 millilitres.^[6] Although derived from the metric system, it is not an SI unit.^[7]

A "coffee cup" is 1.5 dL (i.e. 150 millilitres or 5.07 US customary fluid ounces), and is occasionally used in recipes; in older recipes, cup may mean "coffee cup". It is also used in the US to specify coffeemaker sizes (what can be referred to as a Tasse à café). A "12-cup" US coffeemaker makes 57.6 US customary fluid ounces of coffee, which is equal to 6.8 metric cups of coffee.

Canada now usually employs the metric cup of 250 ml, but its conventional cup was somewhat smaller than both American and imperial units.^{[8][dead link]}

British cookery books and recipes, especially those from the days before the UK's partial metrication, commonly called for a quantity measured by an ordinary vessel, such as a 'tumblerful' of one ingredient and a 'wineglassful' of another one. Unlike the standard US cup, these are not precise units; there is no imperial unit⁠–⁠based culinary measuring cup. Today, recipes normally use imperial fluid ounces or millilitres, and recipes referring to cups are generally assumed either to refer to US cups or to be an inexact measure.^{[citation needed]}

The cookery writer Elizabeth David, writing in The Spectator, referred to several "cups", defining them all as approximate measures, in contrast to the exact US measure: the breakfast cup (8 fl oz),^[9][10] the teacup (5 fl oz),^[9] and the coffee cup (2⁠1/2⁠ fl oz).^[9] Of these, the breakfast cup is the most similar in size to the US standard cup, but is slightly smaller since the US fluid ounce is slightly larger.

The 1894 book Enquire Within Upon Everything defines that 1 cup "usually contains about" 6 imperial fluid ounces (fl oz).^[11] The same book also mentions two culinary measurement units of volume based on drinking vessels: the tumbler (10 fl oz = 1⁄2 imp pint)^[11][12] and the wine glass (2 fl oz).^[11][13] Again, both are approximate, and none are now in common use. Since the UK is not a major producer of wine, typical wine glass sizes are those used by the biggest suppliers of wine, especially EU producers, who exclusively use metric measurements. Common wine glass sizes are 125 or 250 ml, corresponding to 1⁄8 or 1⁄4 respectively of a standard wine bottle (750 ml); but these are not generally used as units.

Similar units in other languages and cultures are sometimes translated "cup", usually with various values around 1⁄5 to 1⁄4 of a litre.

In Latin America, the amount of a "cup" (Spanish: taza) varies from country to country, using a cup of 200 ml (about 7.04 British imperial fluid ounces or 6.76 US customary fluid ounces), 250 ml (about 8.80 British imperial fluid ounces or 8.45 US customary fluid ounces), and the US legal or customary amount.

The traditional Japanese unit equated with a "cup" size is the gō, legally equated with ⁠2,401/13,310⁠ litre (≈ 180.4 ml/6.35 British imperial fluid ounces/6.1 US customary fluid ounces) in 1891, and is still used for reckoning amounts of rice and sake. The Japanese later defined a "cup" as 200 ml.

The traditional Russian measurement system included two cup sizes: the "charka" (cup proper) and the "stakan" ("glass"). The charka was usually used for alcoholic drinks and is 123mL (about 4.33 British imperial fluid ounces or 4.16 US customary fluid ounces), while the stakan, used for other liquids, was twice as big and is 246mL (about 8.66 British imperial fluid ounces or 8.32 US customary fluid ounces).

Since metrication, the charka was informally redefined as 100 ml (about 3.52 British imperial fluid ounces or 3.38 US customary fluid ounces), acquiring a new name of "stopka" (related to the traditional Russian measurement unit "stopa"^{[citation needed]}), while there are currently two widely used glass sizes of 250mL (about 8.80 British imperial fluid ounces or 8.45 US customary fluid ounces) and 200 ml (about 7.04 British imperial fluid ounces or 6.76 US customary fluid ounces).

In The Netherlands, traditionally a "cup" (Dutch: kopje) amounts to 150 ml (about 5.28 British imperial fluid ounces or 5.07 US customary fluid ounces). However, in modern recipes, the US legal cup of 240 ml (about 8.45 British imperial fluid ounces or 8.12 US customary fluid ounces) is more commonly used.

In Europe, recipes normally weigh non-liquid ingredients in grams rather than measuring volume. For example, where an American recipe might specify "1 cup of sugar and 2 cups of milk", a European recipe might specify "200 g sugar and 500 ml of milk". A precise conversion between the two measures takes into account the density of the ingredients, and some recipes specify both weight and volume to facilitate this conversion. Many European measuring cups have markings that indicate the weight of common ingredients for a given volume.

• Cooking weights and measures