|Unit system||imperial/US units|
|1 furlong in ...||... is equal to ...|
|imperial/US units||220 yd|
|metric (SI) units||201.1680 m|
A furlong is a measure of distance in imperial units and U.S. customary units equal to one eighth of a mile, equivalent to 660 feet, 220 yards, 40 rods, 10 chains or approximately 201 metres. In the United States some states use older definitions for surveying purposes, leading to variations in the length of the furlong of two parts per million, or about 0.4 millimetre (1⁄64 inch). This variation is too small to have practical consequences in most applications.
Using the international definition of the yard as exactly 0.9144 metres, one furlong is 201.168 metres and five furlongs are about 1 kilometre (1.00584 km exactly).
The name furlong derives from the Old English words furh (furrow) and lang (long).Dating back at least to early Anglo-Saxon times, it originally referred to the length of the furrow in one acre of a ploughed open field (a medieval communal field which was divided into strips). The furlong (meaning furrow length) was the distance a team of oxen could plough without resting. This was standardised to be exactly 40 rods or 10 chains. The system of long furrows arose because turning a team of oxen pulling a heavy plough was difficult. This offset the drainage advantages of short furrows and meant furrows were made as long as possible. An acre is an area that is one furlong long and one chain (66 feet or 22 yards) wide. For this reason, the furlong was once also called an acre's length, though in modern usage an area of one acre can be of any shape. The term furlong, or shot, was also used to describe a grouping of adjacent strips within an open field.
Among the early Anglo-Saxons, the rod was the fundamental unit of land measurement. A furlong was 40 rods; an acre 4 by 40 rods, or 4 rods by 1 furlong, and thus 160 square rods; there are 10 acres in a square furlong. At the time, the Saxons used the North German foot, which was about 10 percent longer than the foot of the international 1959 agreement. When England changed to a shorter foot in the late 13th century, rods and furlongs remained unchanged, since property boundaries were already defined in rods and furlongs. The only thing that changed was the number of feet and yards in a rod or a furlong, and the number of square feet and square yards in an acre. The definition of the rod went from 15 old feet to 16 1⁄2 new feet, or from 5 old yards to 5 1⁄2 new yards. The furlong went from 600 old feet to 660 new feet, or from 200 old yards to 220 new yards. The acre went from 36,000 old square feet to 43,560 new square feet, or from 4,000 old square yards to 4,840 new square yards.
The furlong was historically viewed as being equivalent to the Roman stade (stadium),which in turn derived from the Greek system. For example, the King James Bible uses the term "furlong" in place of the Greek stadion, although more recent translations often use miles or kilometres in the main text and give the original numbers in footnotes.
In the Roman system, there were 625 feet to the stadium, eight stadia to the mile, and three miles to the league. A league was considered to be the distance a man could walk in one hour, and the mile (from mille, "meaning thousand") consisted of 1,000 passus (paces, five feet, or double-step).
After the fall of the Western Roman Empire, medieval Europe continued with the Roman system, which the people proceeded to diversify, leading to serious complications in trade, taxation, etc. Around the year 1300, by royal decree England standardized a long list of measures. Among the important units of distance and length at the time were the foot, yard, rod (or pole), furlong, and the mile. The rod was defined as 5 1⁄2 yards or 16 1⁄2 feet, and the mile was eight furlongs, so the definition of the furlong became 40 rods and that of the mile became 5,280 feet (eight furlongs/mile times 40 rods/furlong times 16 1⁄2 feet/rod).
A description from 1675 states, "Dimensurator or Measuring Instrument whereof the mosts usual has been the Chain, and the common length for English Measures four Poles, as answering indifferently to the Englishs Mile and Acre, 10 such Chains in length making a Furlong, and 10 single square Chains an Acre, so that a square Mile contains 640 square Acres." —John Ogilby, Britannia, 1675
The official use of the furlong was abolished in the United Kingdom under the Weights and Measures Act 1985, an act that also abolished the official use of many other traditional units of measurement.
In Myanmar, furlongs are currently used in conjunction with miles to indicate distances on highway signs. Mileposts on the Yangon–Mandalay Expressway use miles and furlongs.
In the rest of the world, the furlong has very limited use, with the notable exception of horse racing in most English-speaking countries, including Canada and the United States. The distances for horse racing in Australia were converted to metric in 1972,but in the United Kingdom, Ireland, Canada, and the United States, races are still given in miles and furlongs. Also distances along the canals in English navigated by narrowboats are commonly expressed in miles and furlongs.
The city of Chicago's street numbering system allots a measure of 800 address units to each mile, in keeping with the city's system of eight blocks per mile. This means that every block in a typical Chicago neighborhood (in either north–south or east–west direction but rarely both) is approximately one furlong in length. Salt Lake City's blocks are also each a square furlong in the downtown area. The blocks become less regular in shape farther from the center, but the numbering system (800 units to each mile) remains the same everywhere in Salt Lake County. Blocks in central Logan, Utah, and in large sections of Phoenix, Arizona, are similarly a square furlong in extent (eight to a mile, which explains the series of freeway exits: 19th Ave, 27th, 35th, 43rd, 51st, 59th ...). City blocks in the Hoddle Grid of Melbourne are also one furlong in length.
Much of Ontario, Canada, was originally surveyed on a ten-furlong grid, with major roads being laid out along the grid lines. Now that distances are shown on road signs in kilometres, these major roads are almost exactly two kilometres apart. The exits on highways running through Toronto, for example, are generally at intervals of two kilometres.
The furlong is also a base unit of the humorous FFF system of units.
The exact length of the furlong varies slightly among English-speaking countries. In Canada m. Australia does not formally define the furlong, but it does define the chain and link in terms of the international yard.and the United Kingdom, which define the furlong in terms of the international yard of exactly 0.9144 metres, a furlong is 201.168
In the United States, which defines the furlong, chain, rod, and link in terms of the U.S. survey foot of exactly 1200⁄3937 metre, a furlong is approximately 201.1684 m long. The United States does not formally define a "survey yard". The difference of approximately two parts per million between the U.S. value and the "international" value is insignificant for most practical measurements.
In October 2019, U.S. National Geodetic Survey and National Institute of Standards and Technology announced their joint intent to retire the U.S. survey foot, with effect from the end of 2022. The furlong in U.S. Customary units is thereafter defined based on the International 1959 foot, giving the length of the furlong as exact 201.168 meters in the United States as well.
The acre is a unit of land area used in the imperial and US customary systems. It is traditionally defined as the area of one chain by one furlong, which is exactly equal to 10 square chains, 1⁄640 of a square mile, or 43,560 square feet, and approximately 4,047 m2, or about 40% of a hectare. Based upon the International yard and pound agreement of 1959, an acre may be declared as exactly 4,046.8564224 square metres. The acre was sometimes abbreviated ac, but was often spelled out as the word "acre".
The inch is a unit of length in the (British) imperial and United States customary systems of measurement. It is equal to 1⁄36 yard or 1⁄12 of a foot. Derived from the Roman uncia ("twelfth"), the word inch is also sometimes used to translate similar units in other measurement systems, usually understood as deriving from the width of the human thumb.
The imperial system of units, imperial system or imperial units 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 units replaced the Winchester Standards, which were in effect from 1588 to 1825. The system came into official use across the British Empire in 1826. By the late 20th century, most nations of the former empire had officially adopted the metric system as their main system of measurement, but imperial units are still used in the United Kingdom and some other countries formerly part of the British Empire. The imperial system developed from what were first known as English units, as did the related system of United States customary units.
The mile, sometimes the international mile to distinguish it from other miles, is an imperial unit and US customary unit of length equal to 5,280 feet, or 1,760 yards, and standardised as exactly 1,609.344 metres by international agreement in 1959.
United States customary units are a system of measurements commonly used in the United States since it was formalized in 1832. The United States customary system developed from English units which were in use in the British Empire before the U.S. became an independent country. The United Kingdom's system of measures was overhauled in 1824 to create the imperial system, which was officially adopted in 1826, changing the definitions of some of its units. Subsequently, while many U.S. units are essentially similar to their imperial counterparts, there are significant differences between the systems.
The yard is an English unit of length, in both the British imperial and US customary systems of measurement, that comprises 3 feet or 36 inches. Since 1959 it is by international agreement standardized as exactly 0.9144 meters. 1,760 yards is equal to 1 mile.
A fathom is a unit of length in the imperial and the U.S. customary systems equal to 6 feet (1.8288 m), used especially for measuring the depth of water. The fathom is not an International Standard (SI) unit, nor is it accepted internationally as a non-SI unit. However it is historically the most frequently employed maritime measure of depth in the English speaking world.
The foot (pl. feet), standard symbol: ft, is a unit of length in the British imperial and United States customary systems of measurement. The prime symbol,, is a customarily used alternative symbol. Since the International Yard and Pound Agreement of 1959, one foot is defined as 0.3048 meters exactly. In customary and imperial units, one foot comprises 12 inches and one yard comprises three feet.
A unit of length refers to any arbitrarily chosen and accepted reference standard for measurement of length. The most common units in modern use are the metric units, used in every country globally. In the United States the U.S. customary units are also in use. British Imperial units are still used for some purposes in the United Kingdom and some other countries. The metric system is sub-divided into SI and non-SI units.
The rod or perch or pole is a surveyor's tool and unit of length of various historical definitions, often between 3 and 8 meters. In modern US customary units it is defined as 16 1⁄2 US survey feet, equal to exactly 1⁄320 of a surveyor's mile, or a quarter of a surveyor's chain, and is approximately 5.0292 meters. The rod is useful as a unit of length because whole number multiples of it can form one acre of square measure. The 'perfect acre' is a rectangular area of 43,560 square feet, bounded by sides 660 feet long and 66 feet wide or, equivalently, 40 rods and 4 rods. An acre is therefore 160 square rods or 10 square chains.
The chain is a unit of length equal to 66 feet. It is subdivided into 100 links or 4 rods. There are 10 chains in a furlong, and 80 chains in one statute mile. In metric terms, it is 20.1168 m long. By extension, chainage is the distance along a curved or straight survey line from a fixed commencing point, as given by an odometer.
A system of measurement is a collection of units of measurement and rules relating them to each other. Systems of measurement have historically been important, regulated and defined for the purposes of science and commerce. Systems of measurement in use include the International System of Units (SI), the modern form of the metric system, the British imperial system, and the United States customary system.
Gunter's chain is a distance measuring device used for surveying. It was designed and introduced in 1620 by English clergyman and mathematician Edmund Gunter (1581–1626). It enabled plots of land to be accurately surveyed and plotted, for legal and commercial purposes.
The link, sometimes called a Gunter’s link, is a unit of length formerly used in many English-speaking countries. In US customary units modern definition, the link is exactly 66⁄100 of a US survey foot, or exactly 7.92 inches or approximately 20.12 cm.
English units are the units of measurement used in England up to 1826, which evolved as a combination of the Anglo-Saxon and Roman systems of units. Various standards have applied to English units at different times, in different places, and for different applications.
The earliest recorded systems of weights and measures originate in the 3rd or 4th millennium BC. Even the very earliest civilizations needed measurement for purposes of agriculture, construction, and trade. Early standard units might only have applied to a single community or small region, with every area developing its own standards for lengths, areas, volumes and masses. Often such systems were closely tied to one field of use, so that volume measures used, for example, for dry grains were unrelated to those for liquids, with neither bearing any particular relationship to units of length used for measuring cloth or land. With development of manufacturing technologies, and the growing importance of trade between communities and ultimately across the Earth, standardized weights and measures became critical. Starting in the 18th century, modernized, simplified and uniform systems of weights and measures were developed, with the fundamental units defined by ever more precise methods in the science of metrology. The discovery and application of electricity was one factor motivating the development of standardized internationally applicable units.
Both the British Imperial and United States customary systems of measurement derive from earlier English systems used in the Middle Ages, that were the result of a combination of the local Anglo-Saxon units inherited from German tribes and Roman units brought by William the Conqueror after the Norman Conquest of England in 1066.
There are a number of Spanish units of measurement of length or area that are virtually obsolete due to metrication. They include the vara, the cordel, the league and the labor. The units of area used to express the area of land are still encountered in some transactions in land today. For example, the vara is still used in Costa Rica when ordering lumber.
A rood is a historic English and international inch-pound measure of area, as well as an archaic English measure of length.
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.
footnote 17: heat an acre; run a heat or course of an acre's length, "acre" being used as a lineal measure, equivalent to a furlong.WT 1.2 M