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 appropriate 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, even for dry ingredients. Most of these units derive from earlier
English units, as applied to the
U.S. gallon. Typically they follow a pattern of binary submultiples, where each larger measure consists of two units of the next-smallest measure. An exception is with the commonly used teaspoon as one-third of a tablespoon. 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 similarly down to (1 ) using hieratic notation, as early as the
Fifth Dynasty of Egypt, 2494 to 2345 BC, thus making the "English doubling system" at least 4,300 years old. From units and tools of convenience, most of the system's history could have values vary widely. It was not until recent centuries that standardization began to take shape. The overlap with other systems like the
apothecaries' system, and giving each division a unique and often variable by context, person, place, and time name instead of a systematic one, can make the system seem confusing for those not accustomed to it. Other than the names themselves, the regular ratios make the actual measurements straightforward. In many cases, names have been deprecated in favor of fractionally denominated amounts of a few core units (such as taking gallons, cups, and teaspoons to their nearest quarters without names: nixing pottle; gill and wineglass; dram (as a culinary unit), coffeespoon, and saltspoon; respectively), or are limited to the specific or esoteric. It is still a legal basis for measures in many 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." Metric equivalents are based upon one of two nearly equivalent systems. In the standard system the conversion is that 1 gallon = 231 cubic inches and 1 inch = 2.54 cm, which makes a gallon = 3785.411784 millilitres exactly. For nutritional labeling on food packages in the US, the teaspoon is defined as exactly 5 ml, giving 1 gallon = 3840 ml exactly. This chart uses the former. Suffixed asterisks on some of the "tsp" units in the "Defined" column above indicate that those teaspoon units are defined as fl oz (4 fl dram), the old = amount, instead of . This definition fits with "barkeepers' teaspoon", and is used in many cocktail recipe books. Generally the subdivisions are not so explicitly defined nor named below in general culinary. This can be verified by comparing the associated values in the "fl oz" column. All other "tsp" units in the "Defined" column are indeed defined as , the current = amount. • Discrepancies due to size, generally disregarded as at the scale it becomes a factor, the person generally is using the next size up measuring cup (i.e.: is likely to be straight measured in an ounce cup and not as 9 (vs 12) teaspoons) ‡ Rare if not nonexistent in use by name rather than as fraction of a different unit. † The
fluid scruple has been properly defined on its own in the
apothecaries' system as fl oz, fluid dram, or = 20 minims (≈ 1.23223 ml), and also tsp. Mind that scruples and drams were pharmaceutical and intended to be specific and precise. Cooking measures tended to use what was on hand and/or actually used to consume what was being prepared, and not intended to be as formally scientific in its degree of precision. The
saltspoon most likely combined into the scruple over time, as a consequence of home cooks
approximating standard measures with what they had at hand, much as the teaspoon was roughly "close enough" for a kitchen approximation to a
fluid dram (= 60 minims), but not equal to the fl dr (80 minims) value it actually is. Especially with the variability of the
method of measuring itself. Not of insignificance is the natural habit of customary measures to use a 2n dividing scheme regardless of exact definitions. This pattern is seen even with metric
measuring spoons. Confusion comes about from teaspoon continuing to be called a "dram" in vernacular, despite the sizes of actual spoons creeping up quietly over time, such that of a tsp (tsp > fl dr) would in fact become congruent with current fl dr values for the scruple and saltspoon. In other words, the terminology not keeping pace with the definition. At the small scales involved this is negligible (i.e.: math can convert down to tsp ×10−9, but to what degree can it practically be meted). However, it can cause
problems when accuracy is required such as medicines: "In almost all cases the modern teacups, tablespoons, dessertspoons, and teaspoons, after careful test by the author, were found to average 25 percent greater capacity than the theoretical quantities given above, and thus the use of accurately graduated medicine glasses, which may be had now at a trifling cost, should be insisted upon." • Discrepancies due to size, generally disregarded as at the scale it becomes a factor, the person generally is using the next size up measuring cup. i.e.: is likely to be straight measured in an ounce cup and not as 9 (
vs 12) teaspoons. 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 ( lb) or volume (3 tbsp) or a combination of weight and volume ( 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 lb [113 g], is a
de facto measure in the US. Some recipes may specify butter amounts called a
pat (1–1.5 tsp) or a
knob (2 tbsp). 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 USP—essentially, 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 medicine. == British (Imperial) measures ==