Cooking Weights And Measures - Cups To Liters

In recipes, quantities of ingredients may be specified by mass (commonly called weight), by volume, or by count.

For most of history, most cookbooks did not specify quantities precisely, instead talking of "a nice leg of spring lamb", a "cupful" of lentils, a piece of butter "the size of a walnut", and "sufficient" salt. Informal measurements such as a "pinch", a "drop", or a "hint" (soupçon) continue to be used from time to time. In the US, Fannie Farmer introduced the more exact specification of quantities by volume in her 1896 Boston Cooking-School Cook Book.

Today, most of the world prefers metric measurement by weight, though the preference for volume measurements continues among home cooks in the United States ("almost exclusively"), the rest of North America, and Australia. Different ingredients are measured in different ways:

Liquid ingredients are generally measured by volume worldwide.

Dry bulk ingredients, such as sugar and flour, are measured by weight in most of the world ("250 g flour"), and by volume in North America and Australia ("1/2 cup flour"). Small quantities of salt and spices are generally measured by volume worldwide, as few households have sufficiently precise balances to measure by weight.

Meats are generally specified by weight or count worldwide: "a 2 kg chicken"; "four lamb chops".

Eggs are usually specified by count. Vegetables are usually specified by weight or occasionally by count, despite the inherent imprecision of counts given the variability in the size of vegetables.

Metric measures

In most of the world, recipes use the metric system of unitsâ€"litres (L) and millilitres (mL), grams (g) and kilograms (kg), and degrees Celsius (°C). The spelling litre is preferred in most English-speaking nations: the notable exception is the United States where the spelling liter is preferred.

The USA measures weight in pounds (avoirdupois), while recipes in the UK, following the advice of the Guild of Food Writers, tend to be first in metric quantities and in pounds and ounces or may exclusively be in metric. The USA also uses volume measures based on cooking utensils and pre-metric measures. The actual values frequently deviate from the utensils on which they were based, and there is little consistency from one country to another.

^† In South Australia, a "pint" of beer is traditionally 425 mL, while most other states have metricated this value to 570 mL.

The volumetric measures here are for comparison only. See below for the definition of Gallon for more details.

In addition, the "cook's cup" above is not the same as a "coffee cup" which can vary anywhere from 100 to 200 mL (3.5 to 7.0 imp fl oz; 3.4 to 6.8 US fl oz), or even smaller for espresso.

In Australia â€" since 1970 â€" metric utensil units have been standardized by law and imperial measures no longer have legal status. However â€" it is wise to measure the actual volume of the utensil measures â€" particularly the 'Australian tablespoon' â€" see above â€" since many are imported from other countries with different values. Dessertspoons are standardized as part of the metric system at 10 mL, though they are not normally used in contemporary recipes. Australia is the only metricated country with a metric tablespoon of 20 mL, unlike the rest of the world, which has a 15 mL metric tablespoon.

In Europe older recipes frequently refer to pounds (e.g. Pfund in German, pond in Dutch, livre in French). In each case, the unit refers to 500 g, about 10% more than an avoirdupois pound (454 g). Dutch recipes may also use the ons, which is 100 g.

Weight of liquids

With the advent of accurate electronic scales it has become more common to weigh liquids for use in recipes, avoiding the need for accurate volumetric utensils. The most common liquids used in cooking are water and milk, milk weighing approximately the same as water in the low volumes used in cooking.

1 mL of water weighs 1 gram so a recipe calling for 300 mL (≈ ½ Imperial Pint) of water can simply be substituted with 300 g (≈ 10 oz.) of water.

1 fluid ounce of water weighs approximately 1 ounce so a recipe calling for a UK pint (20 fl oz) of water can be substituted with 20 oz of water.

More accurate weight equivalents become important in the large volumes used in commercial food production. To an accuracy of five significant digits, they are:

Even a home cook can use greater precision at times. Water at 4.0 °C (39.2 °F) may be volumetrically measured then weighed to determine an unknown measuring-utensil volume without the need for a water-density adjustment.

United States measures

The US uses pounds and ounces (avoirdupois) for weight, and US customary units for volume. For measures used in cookbooks published in other nations navigate to the apropos regional section in Traditional measurement systems.

Measures are classified as either dry measures or fluid measures. Some of the fluid and dry measures have similar names, but the actual measured volume is quite different. A recipe will generally specify which measurement is required. U.S. recipes are commonly in terms of fluid measures. Most of these units derive from the English doubling system, whereby each larger measure consists of two units of the next-smallest measure. In the U.S., the doubling system is also called binary submultiples (sometimes binary subdivision).

Binary submultiples are fractional parts obtained by successively dividing by the number 2. Thus, one-half, one-fourth, one-eighth, one-sixteenth, and so on, are binary submultiples. The system can be traced back to the measuring systems of the Hindus and the ancient Egyptians, who subdivided the hekat (about 4.8 litres) into parts of  ¹â„₂,  ¹â„₄, ¹â„₈,  ¹â„₁₆,  ¹â„₃₂, and  ¹â„₆₄ (1 ro, or mouthful, or about 14.5 ml), and the hin similarly down to  ¹â„₃₂ (1 ro) using hieratic notation, as early as the Fifth Dynasty of Egypt, 2494 to 2345 BC, thus making the "English doubling system" at least 4300 years old.

The introduction of measures that don't follow the system, combined with the dropping from common use of a few measures essential to the continuity of the system (dessertspoon, wineglass, and pottle), combined with the redefinition of the teaspoon from  ¹â„₈ to  ¹â„₆ of a fl oz, has gradually left the system little-understood. However, it is still a legal basis for measures in some states, such as Massachusetts, which mandates that "Glass bottles or jars used for the sale of milk or cream to the consumer shall be of the capacity of one gallon, a multiple of the gallon, or a binary submultiple of the gallon."

In domestic cooking, bulk solids, notably flour and sugar, are measured by volume, often cups, though they are sold by weight at retail. Weight measures are used for meat. Butter may be measured by either weight ( ¹â„₄ lb) or volume (3 tbsp) or a combination of weight and volume ( ¹â„₄ lb plus 3 tbsp); it is sold by weight but in packages marked to facilitate common divisions by eye. (As a sub-packaged unit, a stick of butter, at  ¹â„₄ lb [113 g], is a de facto measure in the US)

Cookbooks in Canada use the same system, although pints and gallons would be taken as their Imperial quantities unless specified otherwise. Following the adoption of the metric system, recipes in Canada are frequently published with metric conversions.

Approximate units

There are a variety of approximate units of measures, which are frequently undefined by any official source, or which have had conflicting definitions over time, yet which are commonly used. The measurement units that are most commonly understood to be approximate are the drop, smidgen, pinch, and dash, yet nearly all of the traditional cooking measurement units lack statutory definitions, or even any definition by any organization authorized to set standards in the U.S. For example, of the table above, only the fluid ounce, pint, quart, and gallon are officially defined by the NIST. All of the others appear only in conversion guides lacking statutory authority, or in now-obsolete publications of the U.S. Pharmacopeial Convention, or USPâ€"literally the Apothecaries' system, which still has authority to define certain drug and supplement standards. The USP has long-since abandoned Apothecaries' measurements, and even now recommends against using teaspoons to measure doses of medic ine.

British (Imperial) measures

Note that measurements in this section are in imperial units.

Traditional British measures distinguish between weight and volume.

• Weight is measured in ounces and pounds (avoirdupois) as in the U.S.
• Volume is measured in Imperial gallons, quarts, pints, and fluid ounces. The Imperial gallon was originally defined as 10 pounds (4.5359 kg) of water in 1824, and refined as exactly 4.54609 litres in 1985. Older recipes may well give measurements in cups; insofar as a standard cup was used, it was usually  ¹â„₂ pint [~285 mL] (or sometimes  ¹â„₃ pint [~190 mL]), but if the recipe is one that has been handed down in a family, it is just as likely to refer to someone's favourite kitchen cup as to that standard.

American cooks using British recipes, and vice versa, need to be careful with pints and fluid ounces. A US pint is 473 mL, while a UK pint is 568 mL, about 20% larger. A US fluid ounce is  ¹â„₁₆ of a US pint (29.6 mL); a UK fluid ounce is  ¹â„₂₀ UK pint (28.4 mL). This makes an Imperial pint equivalent to 19.2 US fluid ounces.

On a larger scale, perhaps for institutional cookery, an Imperial gallon is eight Imperial pints (160 imp fl oz, 4.546 litres) whereas the US gallon is eight US pints (128 US fl oz, 3.785 litres).

The metric system was officially adopted in the UK, for most purposes, in the 20th century and both imperial and metric are taught in schools and used in books. It is now mandatory for the sale of food to also show metric. However, it is not uncommon to purchase goods which are measured and labeled in metric, but the actual measure is rounded to the equivalent imperial measure (i.e., milk labeled as 568 mL / 1 pint). In September 2007, the EU with Directive 2007/45/EC deregulated prescribed metric packaging of most products, leaving only wines and liqueurs subject to prescribed EU-wide pre-packaging legislation; the law relating to labelling of products remaining unchanged.

Special instructions

Volume measures of compressible ingredients have a substantial measurement uncertainty, in the case of flour of about 20%. Some volume-based recipes, therefore, attempt to improve the reproducibility by including additional instructions for measuring the correct amount of an ingredient. For example, a recipe might call for "1 cup brown sugar, firmly packed", or "2 heaping cups flour". A few of the more common special measuring methods:

Firmly packed

With a spatula, a spoon, or by hand, the ingredient is pressed as tightly as possible into the measuring device.

Lightly packed

The ingredient is pressed lightly into the measuring device, only tightly enough to ensure no air pockets.

Even / level

A precise measure of an ingredient, discarding all of the ingredient that rises above the rim of the measuring device. Sweeping across the top of the measure with the back of a straight knife or the blade of a spatula is a common leveling method.

Rounded

Allowing a measure of an ingredient to pile up above the rim of the measuring device naturally, into a soft, rounded shape.

Heaping / heaped

The maximum amount of an ingredient which will stay on the measuring device.

Sifted

This instruction may be seen in two different ways, with two different meanings: before the ingredient, as "1 cup sifted flour", indicates the ingredient should be sifted into the measuring device (and normally leveled), while after the ingredient, as "1 cup flour, sifted", denotes the sifting should occur after measurement.

Such special instructions are unnecessary in weight-based recipes.