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The former Weights and Measures office in Seven Sisters, London (590 Seven Sisters Road). The imperial system of units, imperial system or imperial units (also known as British Imperial [1] or Exchequer Standards of 1826) is the system of units first defined in the British Weights and Measures Act 1824 and continued to be developed through a series of Weights and Measures Acts and amendments.
The imperial and US customary systems of measurement use the SI for their formal definitions, the yard being defined as 0.9144 metres exactly, the pound avoirdupois as 0.453 592 37 kilograms exactly while both systems of measure share the definition of the second.
The stone is not a measurement of weight used in the US. The US customary system uses the short hundredweight of 100 lb and short ton of 2,000 lb. Where these systems most notably differ is in their units of volume. An imperial fluid ounce of 28.4130625 ml is 3.924% smaller than the US fluid ounce (fl oz) of 29.5735295625 millilitres (ml).
In 1824, these units were replaced with a single system based on the imperial gallon. [ a ] Originally defined as the volume of 10 pounds (4.54 kg) of distilled water (under certain conditions) [ b ] , then redefined by the Weights and Measures Act 1985 to be exactly 4.546 09 L (≈277.42 cu in), the imperial gallon is 1.62% smaller than the ...
The informal public imperial measurement standards erected at the Royal Observatory, Greenwich, London, in the 19th century: 1 British yard, 2 feet, 1 foot, 6 inches, and 3 inches. The inexact monument was designed to permit rods of the correct measure to fit snugly into its pins at an ambient temperature of 62°F (16 2 ⁄ 3 °C).
The basic unit of length in the imperial and U.S. customary systems is the yard, defined as exactly 0.9144 m by international treaty in 1959. [2] [10] Common imperial units and U.S. customary units of length include: [11] thou or mil (1 ⁄ 1000 of an inch) inch (25.4 mm) foot (12 inches, 0.3048 m) yard (3 feet, 0.9144 m)
The pound or pound-mass is a unit of mass used in both the British imperial and United States customary systems of measurement.Various definitions have been used; the most common today is the international avoirdupois pound, which is legally defined as exactly 0.453 592 37 kilograms, and which is divided into 16 avoirdupois ounces. [1]
The modern statutory definition of Imperial units, the Weights and Measures Act 1985 as amended by The Units of Measurement Regulations 1994, defines the quarter as a unit of mass equal to 28 pounds. [6] In measures of weight and mass at the time of Magna Carta, the quarter was 1 ⁄ 4 ton or (originally 500 pounds).