page_title: Imperial and US customary measurement systems
section_title: Imperial units
hierarchical_section_title: Imperial and US customary measurement systems / Imperial units
caption_attribution_description: English: Leaving St. Columb. Signpost at a junction on the old road from St. Columb to Wadebridge, a mile from St. Columb.
context_page_description: The Imperial and US customary measurement systems are both derived from an earlier English system of measurement which in turn can be traced back to Ancient Roman units of measurement, and Carolingian and Saxon units of measure.
  The US Customary system of units was developed and used in the United States after the American Revolution, based on a subset of the English units used in the Thirteen Colonies. The Imperial system of units was developed and used in the United Kingdom and its empire beginning in 1826. US Customary units are the predominant system of units in the United States and the metric system has, to varying degrees, replaced the imperial system in the countries that used it.
  Most of the units of measure have been adapted in one way or another since the Norman Conquest. The units of linear measure have changed the least – the yard and the chain were measures derived in England. The foot used by craftsman supplanted the longer foot used in agriculture. The agricultural foot was reduced to ​¹⁰⁄₁₁ of its former size, causing the rod, pole or perch to become ​16 ¹⁄₂ agricultural feet.
context_section_description: The British Weights and Measures Act of 1824 repealed all existing British weights and measures legislation, some dating back to the 1300s, and redefined existing units of measure. In particular, a new standard yard and troy pound were manufactured as the standards for length and weight respectively. A new measure, the imperial gallon, which replaced the many gallons in use, was defined as being the volume of 10 pounds of water at 62 °F which, after the authorized experiments, was found to be 277.274 cubic inches. The bushel, which like the gallon, had definitions reflecting the various gallons, was defined as 8 imperial gallons.
  The 1824 Act also introduced some changes to the administration of the standards of weights and measures: previously Parliament had been given the custody of the standards but the act passed this responsibility on to the Exchequer. The act also set up an inspectorate for weights and measures.
  The standard yard and pound were lost in 1834 when a fire partially destroyed the Palace of Westminster. Following a report published in 1841 by a commission new standard yard and pound were manufactured using the best available secondary sources. Unlike the previous standard, the new pound standard was a pound avoirdupois. They were accepted by an Act of Parliament as the standards for length and weight in 1855. Following the debacle over the different gallons that had been adopted by the United States and the United Kingdom thirty years earlier, one of the copies of the standard yard was offered to and accepted by the United States Government.
  The 1835 Weights and Measures Act tidied up a number of shortcomings in the 1825 Act. In response to representations from traders, the stone and the hundredweight were formally defined as being 14 pounds and 112 pounds respectively and the experiment of defining a "heaped" measure as outlined in the 1824 Act was abandoned. Not all trades followed the use of the 14 stone—Britten, in 1880 for example, catalogued a number of different values of the stone in various British towns and cities ranging from 4 lb to 26 lb The 1835 Act also restricted the use of Troy measure to precious metals and required that coal be sold by weight and not by volume.
  The Weights and Measures Act of 1878 overhauled the inspection regime of weights and measures used in trade. The act also reaffirmed the use of the brass standard yard and platinum standard pound as the standards for use in the United Kingdom, reaffirmed the use of apothecaries measures in the pharmaceutical industry, reaffirmed the 1824 definition of the gallon, removed the Troy pound from the list of legal units of measure, added the fathom to the list of legal units and fixed the ratio of metric to imperial units at one metre being equal to 39.3708 inches and one kilogram being equal to 15432.3487 grains (1 lb = 0.453592654 kg). Subsequent to the passing of the act, the volume of the gallon which had been defined as being the volume of 10 lb distilled water at 62 °F (17 °C) was remeasured and set at 277.42 cubic inches though HM Customs and Excise continued to use the 1824 definition for excise purposes.
  The Weights and Measures Act of 1878 effectively prohibited the use of metric weights for trade, the United Kingdom having declined to sign the Convention of the Metre three years previously. The standard imperial yard was not stable – in 1947 its rate of shrinkage was quantified and found to be one part per million every 23 years. In April 1884 HJ Chaney, Warden of Standards in London unofficially contacted the BIPM (custodians of the standard metre) inquiring whether the BIPM would calibrate some metre standards that had been manufactured in the United Kingdom. Broch, director of the BIPM replied that he was not authorised to perform any such calibrations for non-member states. On 17 September 1884, the British Government signed the convention on behalf of the United Kingdom. The Weights and Measures Act of 1897 authorized the use of metric units for trade; a list of metric to imperial equivalents being published the follo
caption: Road distance signs in the United Kingdom use miles.
exif: {}