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The Imperial units are an irregularly standardized system of units that have been used in the United Kingdom and its former colonies, including the Commonwealth countries. The Imperial system is also called the English system or the British system. It is the primary alternative to the metric system.1 Current use of Imperial units
Today the Imperial units are widely used only in the United States, under the name of the U.S. customary units (and in some cases with different definitions, as discussed below). They have been replaced elsewhere by the SI (metric) system. Most Commonwealth countries have switched entirely to the SI system of units. The United Kingdom completed its legal transition to SI units in 1995, but a few such units are still in official use: for example, beer may still be sold in pints; most roadsign distances are still in yards and miles, and speed limits are in miles per hour. The use of SI units is increasingly mandated by law for the retail sale of food and other commodities, but most British people still use Imperial units in colloquial discussion of distance (miles and yards), speed (miles per hour), weight (stones and pounds) and height (feet and inches). In Ireland, roadsign distances are indicated in kilometres, while speed limits are still indicated in miles per hour.
2 Relation to other systems
Most Imperial units had the same names as to the units that are still predominantly used in the United States (see U.S. customary units). Unfortunately, the detailed definitions differed, and in some cases the differences are substantial.
A further difference between the systems in use in the two countries is that in cooking weights and measures, much more use is made of volume measures (cups and spoons) in the US, whereas in the UK quantities of dry ingredients are usually specified by weight; cup and spoon measurements are sometimes given, but these are not the same as the US standard cups and spoons, and in traditional recipes probably just reflect a favourite cup that the cook had on hand.
In addition, although most of the units were defined in both systems, some subsidiary units were used to a much greater extent, or for different purposes, in one system rather than the other.
3 Measures of length
After the July 1, 1959 deadline, agreed upon in 1958, the U.S. and the British inch were defined identically (25.4 mm) for scientific work and were identical in commercial usage (however, the U.S. retained the slightly different survey inch for specialized surveyingSurveying is concerned with the accurate measurement and position of points on the Earth's surface, and to the establishment of boundaries. It basically achieves this by measuring the relative horizontal and vertical position of points on the ground, aide purposes). The main parts of the tables of length (inch, footA foot is a non- SI unit of distance or length. The popular belief is that original standard was the length of a man's foot. The average foot length is about 240 mm (9. 4 in) for current Europeans. About 996 of 1000 British men have a foot that is less th, yardThis article is about the unit of measure known as the yard''. For other definitions, see Yard (disambiguation). A yard (abbr. yd is an imperial unit of length, defined as 3 feet or 36 inches, which is exactly 0. 9144 metres, presuming international inche and international mileA mile is any of several units of distance, or, as physicists say, of length. Today, one mile is mainly equal to about 1609 metres on land and 1852 metres at sea and in the air, but see below for the details. Current definitions The meanings of mile that) were the same in both countries, though some of the intermediate units such as the chainAs a unit of measurement within the Imperial system, the chain was defined as 22 yards, or 66 feet. Ten chains therefore made one furlong. In metric units, a chain equals 20. 1168 metres. The unit was little used in everyday life even in the heydey of Imp (22 yards) and the furlong (220 yards) were more used in Britain and the Commonwealth than in the U.S.
The full table is as follows:
- 1 barleycorn = 1/3 inch = 8.4¯6 mm
- 1 inch = 2.54 cm
- 1 foot = 12 inches = 3.048 dm
- 1 yard = 3 feet = 9.144 dm
- 1 rod, pole or perch = 5½ yards = 5.0292 m
- 1 chain = 4 poles = 2.01168 dam
- 1 furlong = 10 chains = 2.01168 hm
- 1 mile = 8 furlongs = 1.609344 km
- 1 league = 3 miles = 4.828032 km
However, the nautical mile equalled 6080 feet (1.853184 km), not readily expressible in terms of any of the intermediate units (because it was defined in terms of the circumference of the earth). Depth of water at sea was expressed in fathoms (6 feet = 1.8288 m).
