The quart (symbol: qt)[1] is a unit of volume equal to a quarter of a gallon. Three kinds of quarts are currently used: the liquid quart and dry quart of the US customary system and the imperial quart of the British imperial system. All are roughly equal to one liter. It is divided into two pints or (in the US) four cups. Historically, the size of a quart has varied with the different values of gallons over time, and in the case of the dry quart, in reference to different commodities.
Name
The term comes from the Latinquartus (meaning one-quarter) via the Frenchquart. However, although the French word quart has the same root, it frequently means something entirely different. In Canadian French in particular, the quart is called pinte,[2] while the pint is called chopine.[2]
Since gallons of various sizes have historically been in use, the corresponding quarts have also existed with various sizes.
Definitions and equivalencies
Imperial quart
The imperial quart is equal to one-quarter of an imperial gallon of exactly 4.54609 L, i.e. 1.1365225 L. In the United Kingdom, goods may be sold by the quart if the equivalent metric measure is also given.[3]
In the United States, traditional length and volume measures have been legally standardized for commerce by the international yard and pound agreement of 1959, using the definition of 1 yard being 0.9144 meters: from this definition the metric equivalents for inches, feet, miles, area measures, and measures of volume are determined. The US liquid quart is equal to one-quarter of a gallon of exactly 231 cubic inches, i.e. 57.75 cubic inches or 0.946352946 L.[6][7]
In the United States, the dry quart is equal to 1/32 of a US bushel of exactly 2150.42 cubic inches, i.e. 67.200625 cubic inches or 1.101220942715 L.
The Winchester quart is an obsolescent measure:[10] it was originally equal to two imperial quarts (half of an imperial gallon) or exactly 2.273045 L, but was later metricated to 2.5 L (2.2 imperial quarts). Despite its name, it is unrelated to the Winchester measure.[11]
The 2.5L bottles in which laboratory chemicals are supplied are sometimes referred to as Winchester quart bottles, although these contain 10% more than a traditional Winchester quart.
Reputed quart
The reputed quart was a measure equal to two-thirds of an imperial quart (one-sixth of an imperial gallon), or exactly 0.7576816 liters, which is only 0.08% larger than one US fifth (exactly 0.7570823568 liters).
The reputed quart was previously recognized as a standard size of wine bottle in the United Kingdom, and is only about 1% larger than the current standard wine bottle of 0.75L.[12][13]
Notes
^This has been the exact conversion since the redefinition of the imperial gallon in 1976 in the UK,[4] and in 1964 in Canada.
References
^BS350:Part 1:1974 Conversion factors and tables Part 1. Basis of tables. Conversion factors. British Standards Institution. 1974. pp. 10, 86.
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