This is a list ofunits of measurement in active use, which do not form part of acoherent system of measurement. Many of the items listed here are colloquial units based on familiar objects such as parts of the body. Many of the listed units are approximate or vaguely defined. Some are odd multiples or fractions of a base unit.
Button sizes are typically measured inligne, which can be abbreviated as L. The measurement refers to the button diameter, or the largest diameter of irregular button shapes. There are 40 lignes in 1 inch.[1][2]
Ingroff/troff and specifically in the included traditional manuscript macro setms, the vee (v) is a unit of vertical distance often—but not always—corresponding to the height of an ordinary line of text.[3]
Horizontal pitch (HP) is a unit of length defined by theEurocard printed circuit board standard used to measure the horizontal width of rack-mounted electronic equipment, similar to the rack unit (U) used to measure vertical heights of rack-mounted equipment. One HP is 0.2 inches (1⁄5″) or5.08 millimetres wide.
Valve'sSource game engine uses theHammer unit as its base unit of length. This unit refers to Source's official map creation software, Hammer.[4] The exact definition varies from game to game, but a Hammer unit is usually defined as sixteenth of a foot (16 Hammer units = 1 foot) relative to the map, or 1 inch or 2.54 centimeters when compared to the average player height.[5] With the sixteenth of a foot definition, this means that 1 Hammer unit is equal to exactly19.05 millimetres or0.75 inches (3⁄4″).[6]
Onerack unit (U) is 1.75 inches (44.45 mm) and is used to measure rack-mountable audiovisual, computing and industrial equipment. Rack units are typically denoted without a space between the number of units and the 'U'. Thus, a 4Userver enclosure (case) is nominally seven inches (177.8 mm) high, or more precisely, built to occupy a vertical space seven inches high, with sufficient clearance to allow movement of adjacent hardware.
Thehand is a non-SI unit of length equal to exactly 4 inches (101.6 mm). It is normally used to measure the height of horses in some English-speaking countries, including Australia,[7] Canada, Ireland, the United Kingdom, and the United States. It is customary when measuring in hands to use a point to indicateinches (quarter-hands) and nottenths of a hand. For example, 15.1 hands normally means 15 hands, 1 inch (5 ft 1 in), rather than15+1⁄10 hands.[8]
The light-nanosecond is defined as exactly 29.9792458 cm. It was popularized ininformation technology as a unit of distance byGrace Hopper as the distance which a photon could travel in one billionth of a second (roughly 30 cm or one foot): "Thespeed of light is one foot per nanosecond."[9][10]
A metric foot, defined as 300 millimetres (approximately 11.8 inches), has been used occasionally in the UK but has never been an official unit.[11]
The corresponding metric inch of 25 millimetres (0.984 in) was used for pin spacing in Soviet microchips, which were often cloned from Western designs but scaled down slightly from US customary inches to metric inches. This led to incompatibility issues in the Soviet computer market.[12]
AChinese foot is around one third of a metre, with the exact definition depending on jurisdiction.
Horses are used to measure distances inhorse racing – ahorse length (shortened to merely alength when the context makes it obvious) equals roughly 8 feet or 2.4 metres. Shorter distances are measured in fractions of ahorse length; also common are measurements of a full or fraction of ahead, aneck, or anose.[13]
In rowing races such as theOxford and Cambridge Boat Race, the margin of victory or defeat is expressed in fractions and multiples ofboat lengths. The length of arowing eight is about 62 feet (19 m). This is also commonly expressed in timei.e. 3 or 3.5 seconds. A shorter distance is thecanvas, which is the length of the covered part of the boat between the bow and the bow oarsman, and equivalent to less than one second. TheRacing Rules of Sailing also makes heavy use of boat lengths.
A football field is often used as a comparative measurement of length when talking about distances that may be hard to comprehend when stated in terms of standard units.
AnAmerican football field is usually understood to be 100 yards (91 m) long, though it is technically 120 yards (110 m) when including the two 10 yd (9.1 m) long end zones. The field is 160 ft (53 yd; 49 m) wide.[14]
Anassociation football pitch may vary within limits of 90–120 m (98–131 yd) in length and 45–90 m (49–98 yd) in width. The recommended field size is 105 m × 68 m (115 yd × 74 yd) for major competitions such as theFIFA World Cup,UEFA European Championship andUEFA Champions League.
ACanadian football field is 65 yd (59 m) wide and 150 yd (140 m) long, including two 20 yd (18 m) long end zones.
In most US cities, acity block is between1⁄16 and1⁄8 mi (100 and 200 m). InManhattan, the measurement "block" usually refers to a north–south block, which is1⁄20 mi (80 m). Sometimes people living in places (like Manhattan) with a regularly spaced street grid will speak oflong blocks andshort blocks. Within a typical large North American city, it is often only possible to travel along east–west and north–south streets, so travel distance between two points is often given in the number of blocks east–west plus the number north–south (known to mathematicians as theManhattan Metric).[15]
The globally-averageradius of Earth, generally given as 6,371 kilometres (3,959 miles), is often employed as a unit of measure to intuitively compare objects of planetary size.
Lunar distance (LD), the distance from the centre of Earth to the centre of the Moon, is a unit of measure in astronomy. The lunar distance is approximately 384,400 km (238,900 mi), or 1.28light-seconds; this is roughly 30 timesEarth's diameter. A little less than 400 lunar distances make up anastronomical unit.
Thesiriometer is an obsolete astronomical measure equal to one millionastronomical units, i.e., one million times the average distance between the Sun and Earth.[16] This distance is equal to about 15.8 light-years, 149.6 Pm, or 4.8 parsecs, and is about twice the distance from Earth to the starSirius.[17]
One barn is 10−28 square metres, about the cross-sectional area of a uranium nucleus. The name probably derives from early neutron-deflection experiments, when the uranium nucleus was described, and the phrases "big as a barn" and "hit a barn door" were used. Barn are typically used forcross sections in nuclear and particle physics. Additional units include the microbarn (or "outhouse")[18] and the yoctobarn (or "shed").[19][20]
A kuang is a traditional Chinese unit of area equal to 0.11 square metres or one squareChinese foot.[21]
One brass is exactly 100 square feet (9.29 m2) area (used in measurement of work done or to be done, such as plastering, painting, etc.). The same word is used, however, for 100 cubic feet (2.83 m3) of estimated or supplied loose material, such as sand, gravel, rubble, etc. This unit is prevalent in the construction industry inIndia.[22][23]
The same area is called asquare in the construction industry in North America,[24] and was historically used inAustralia by real estate agents. Aroof's area may be calculated in square feet, then converted to squares.
In Ireland, before the 19th century, a "cow's grass" was a measurement used by farmers to indicate the size of their fields. A cow's grass was equal to the amount of land that could produce enough grass to support a cow.[25][26]
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Afootball pitch, or field, can be used as a man-in-the-street unit of area.[27][28] The standardFIFAfootball pitch for international matches is 105 m (344 ft) long by 68 m (223 ft) wide (7,140 m2 or 0.714 ha or 1.76 acres); FIFA allows for a variance of up to 5 m (16.4 ft) in length in either direction and 7 m (23.0 ft) more or 4 m (13.1 ft) less in width (and larger departures if the pitch is not used for international competition), which generally results in the association football pitch generally only being used fororder of magnitude comparisons.[29]
AnAmerican football field, including both end zones, is 360 by 160 ft (120.0 by 53.3 yd; 109.7 by 48.8 m), or 57,600 square feet (5,350 m2) (0.535 hectares or 1.32 acres). ACanadian football field is 65 yards (59 m) wide and 110 yards (100 m) long with end zones adding a combined 40 yards (37 m) to the length, making it 87,750 square feet (8,152 m2) or 0.8215 ha (2.030 acres).
AnAustralian rules football field may be approximately 150 metres (160 yd) (or more) long goal to goal and 135 metres (148 yd) (or more) wide, although the field's elliptical nature reduces its area to a certain extent. A 150-by-135-metre (164 by 148 yd) football field has an area of approximately 15,900 m2 (1.59 ha; 3.9 acres), twice the area of a Canadian football field and three times that of an American football field.
Amorgen ("morning" in Dutch and German) was approximately the amount of land tillable by one man behind an ox in the morning hours of a day. This was an official unit of measurement in South Africa until the 1970s, and was defined in November 2007 by the South African Law Society as having a conversion factor of 1 morgen =0.856532 hectares.[30] This unit of measure was also used in the Dutch colonial province ofNew Netherland (laterNew York and parts ofNew England).[31][32]
The area of a familiar country, state or city is often used as a size reference, especially injournalism. Usually the region is used to describe something of similar size to the reference region, but in some cases such references become common enough that multiples of the area start to be used, as in "twice the area ofWales".[33][34][35] Besides Wales (20,779 km2 (8,023 sq mi)), other regions that have been used this way includeBelgium (30,528 km2 or 11,787 mi2),[36] the German state ofSaarland (2,569.69 km2 or 992.16 mi2),[37] andWashington, D.C. (61.4 mi2 or 159 km2).[38]
A metric ounce is an approximation of the imperial ounce, US dry ounce, or US fluid ounce. These three customary units vary. However, the metric ounce is usually taken as 25 or 30 ml (0.88 or 1.06 imp fl oz; 0.85 or 1.01 US fl oz) when volume is being measured, or in grams when mass is being measured.
The USFood and Drug Administration (FDA) defines the "food labeling ounce" as 30.0 ml (1.06 imp fl oz; 1.01 US fl oz), slightly larger than the 29.6 ml (1.04 imp fl oz; 1.00 US fl oz)fluid ounce.[39]
SeveralDutch units of measurement have been replaced with informal metric equivalents, including theons or ounce. It originally meant1⁄16 of a pound, or a little over 30 g (1.1 oz) depending on which definition of the pound was used, but was redefined as 100 g (3.5 oz) when the country metricated.[40]
Theshot is a liquid volume measure that varies from country to country and state to state depending on legislation. It is routinely used for measuring strongliquor or spirits when the amount served and consumed is smaller than the more common measures of alcoholic "drink" and "pint". There is a legally defined maximum size of a serving in some jurisdictions. The size of a "single" shot is 20–60 ml (0.70–2.11 imp fl oz; 0.68–2.03 US fl oz). The smaller "pony" shot is 20–30 ml (0.70–1.06 imp fl oz; 0.68–1.01 US fl oz). According to Encyclopædia Britannica Almanac 2009, a pony is 0.75fluid ounces[clarification needed] of liquor.[41] According toWolfram Alpha, one pony is 1 U.S. fluid ounce.[42] "Double" shots (surprisingly not always the size of two single shots, even in the same place) are 40–100 ml (1.4–3.5 imp fl oz; 1.4–3.4 US fl oz). In the UK, spirits are sold in shots of either 25 ml (0.88 imp fl oz; 0.85 US fl oz) (approximating the oldfluid ounce) or 35 ml (1.2 imp fl oz; 1.2 US fl oz).[43]
A board foot is a United States and Canadian unit of approximate volume, used for lumber. It is equivalent to1 inch × 1 foot × 1 foot (144 in3 or 2,360 cm3). It is also found in the unit of densitypounds per board foot. In Australia and New Zealand the termssuper foot orsuperficial foot were formerly used for this unit. The exact volume of wood specified is variable and depends on the type of lumber. For planed lumber the dimensions used to calculate board feet arenominal dimensions, which are larger than the actual size of the planed boards. SeeDimensional lumber for more information on this.
A system of measure for timber in the round (standing or felled), now largely superseded by the metric system except in measuring hardwoods in certain countries. Its purpose is to estimate the value of sawn timber in a log, by measuring the unsawn log and allowing for wastage in the mill. Following the so-called "quarter-girth formula" (the square of one quarter of the circumference in inches multiplied by1⁄144 of the length in feet), the notional log is four feet in circumference, one inch of which yields the hoppus board foot, 1 foot yields the hoppus foot, and 50 feet yields a hoppus ton. This translates to a hoppus foot being equal to 1.273 cubic feet (2,200 in3; 0.0360 m3). The hoppus board foot, when milled, yields about oneboard foot. The volume yielded by the quarter-girth formula is 78.54% of cubic measure (i.e. 1 ft3 = 0.7854 h ft; 1 h ft = 1.273 ft3).[44]
A cubic ton is an antiquated measure of volume, varying based on the commodity from about 16 to 45 ft3 (0.45 to 1.27 m3). It is now only used for lumber, for which one cubic ton is equivalent to 40 ft3 (1.1 m3).
The cord is a unit of measure ofdry volume used in Canada and the United States to measurefirewood andpulpwood. A cord is the amount of wood that, when "ranked and well stowed" (arranged so pieces are aligned, parallel, touching and compact), occupies a volume of 128 cubic feet (3.62 m3).[45] This corresponds to a well-stacked woodpile, 4 feet deep by 4 feet high by 8 feet wide(122 cm × 122 cm × 244 cm), or any other arrangement of linear measurements that yields the same volume. A more unusual measurement for firewood is the "rick" orface cord. It is stacked 16 inches (40.6 cm) deep with the other measurements kept the same as a cord, making it1⁄3 of a cord; however, regional variations mean that its precise definition is non-standardized.[46]
The twenty-foot equivalent unit is the volume of the smallest standardshipping container. It is equivalent to 1,172 cubic feet (33.2 m3). Larger intermodal containers are commonly described in multiples of TEU, as are container ship capacities.
An acre-foot is a unit of volume commonly used in the United States in reference to large-scale water resources, such as reservoirs, aqueducts, canals, sewer flow capacity, irrigation water[47] and river flows. It is defined by the volume of one acre of surface area to a depth of one foot. 43,560 ft3 (1,233 m3; 325,851 US gal; 271,328 imp gal).
Many well-known objects are regularly used as casual units of volume. They include:
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The volume of water which flows in one unit of time through an orifice of one square inch area. The size of the unit varies from one place to another.
It is common in particle physics to use eV/c2 as a unit of mass. Here, eV (electronvolt) is a unit of energy (the kinetic energy of anelectron accelerated over onevolt,1.6×10−19 J), andc is the speed of light in vacuum. Energy and mass are related throughE = mc2. This definition is useful for alinear particle accelerator when accelerating electrons.
In many systems ofnatural unitsc = 1, so thec is dropped and eV itself becomes a unit of mass.
In 1793, the French term "grave" (from "gravity") was suggested as the base unit of mass for the metric system. In 1795, however, the name "kilogramme" was adopted instead.
The mass of an old bag ofcement was onehundredweight (112 pounds, 51 kg). In the concrete and petroleum industry, however, a bag of cement is defined as 94 lb (43 kg) because it has an apparent volume close to 1 cubic foot (28 litres).[63] Whenready-mix concrete is specified, a "bag mix" unit is used as if the batching company mixes 5 literal bags of cement per cubic yard (or cubic metre) when a "5 bag mix" is ordered.[citation needed]
When reporting on the masses ofextrasolar planets, astronomers often discuss them in terms of multiples ofJupiter's mass (MJ = 1.9×1027 kg).[64] For example, "Astronomers recently discovered a planet outside our Solar System with a mass of approximately 3 Jupiters." Furthermore, the mass of Jupiter is nearly equal to one thousandth of the mass of the Sun.
Solar mass (M☉ =2.0×1030 kg) is also often used in astronomy when talking about masses of stars or galaxies; for example,Alpha Centauri A has the mass of 1.1 suns, and theMilky Way has a mass of approximately 6×1011 M☉.
Solar mass also has a special use when estimating orbital periods and distances of 2 bodies usingKepler's laws:a3 = MtotalT2, wherea is length ofsemi-major axis inAU,T is orbital period in years andMtotal is the combined mass of objects inM☉. In case of planet orbiting a star,Mtotal can be approximated to mean the mass of the central object. More specifically in the case of Sun and Earth the numbers reduce toMtotal ~ 1,a ~ 1 andT ~ 1.
George Gamow discussed measurements of time such as the "light-mile" and "light-foot", the time taken for light to travel the specified unit distance, defined by "reversing the procedure" used in defining a light-year.[65] A light-foot is roughly onenanosecond, and one light-mile is approximately fivemicroseconds.[66]
Innuclear engineering and astrophysics contexts, theshake is sometimes used as a conveniently short period of time. 1 shake is defined as 10 nanoseconds.[67]
Incomputing, thejiffy is the duration of one tick of the system timerinterrupt. Typically, this time is 0.01 seconds, though in some earlier systems (such as theCommodore8-bit machines) the jiffy was defined as1⁄60 of a second, roughly equal to the vertical refresh period (i.e. the field rate) onNTSC video hardware (and theperiod of AC electric power in North America).
The term "minute" usually means1⁄60 of anhour, coming from "a minute division of an hour". The term "second" comes from "thesecond minute division of an hour", as it is1⁄60 of a minute, or1⁄60 of1⁄60 of an hour. While usually sub-second units are represented withSI prefixes on the second (e.g.milliseconds), this system can be extrapolated further, such that a "third" would mean1⁄60 of a second (16.7 milliseconds), and a "fourth" would mean1⁄60 of a third (278 microseconds), etc. These units are occasionally used in astronomy to denote angles.[68]
Amoment was amedieval unit of time. The movement of a shadow on asundial covered 40 moments in asolar hour. An hour in this case meant one twelfth of the period betweensunrise andsunset. The length of asolar hour depended on the length of the day, which in turn varied with theseason, so the length of a moment in modernseconds was not fixed, but onaverage, a moment corresponded to 90 seconds.
Thesidereal day is based on the Earth's rotation rate relative to fixed stars, rather than the Sun. A sidereal day is approximately 23 hours, 56 minutes, 4.0905 SI seconds.
There have been numerous proposals and usage of decimal time, most of which were based on the day as the base unit. In dynastic China, thekè was a unit that represented1⁄100 of a day (since redefined to1⁄96 of a day, or 15 minutes). In France, a decimal time system in place from 1793 to 1805 divided the day into 10 hours, each divided into 100 minutes, in turn divided into 100 seconds; theFrench Republican calendar further extended this by assembling days into ten-day weeks.
Ordinal dates andJulian days, the latter of which has seen use in astronomy as it is not subject toleap year complications, allow for the expression of a decimal portion of the day.[69] In the mid-1960s, to defeat the advantage of the recently-introduced computers for the then-popular rally racing in the Midwest, competition lag times in a few events were given incentids (1⁄100 day, 864 seconds, 14.4 minutes),millids (1⁄1,000 day, 86.4 seconds), andcentims (1⁄100 minute, 0.6 seconds) the latter two looking and sounding a bit like the related units of minutes and seconds.[verification needed] Decimal time is frequently found in fiction, often infuturistic works.
TheSwatch Internet Time system is based on decimal time.
Many mechanicalstopwatches are of the 'decimal minute' type. These split one minute into 100 units of 0.6 s each. This makes addition and subtraction of times easier than using regular seconds.
Hexadecimal time divides the day into 16 hexadecimal hours, each hour into 256 hexadecimal minutes, and each minute into 16 hexadecimal seconds.
The United States-basedNASA, when conducting missions to the planetMars, has typically used a time of day system calibrated to the mean solar day on that planet (known as a "sol"), training those involved on those missions to acclimate to that length of day, which is 88,775 SI seconds, or 2,375 seconds (about 39 minutes) longer than the mean solar day on Earth. NASA's Martian timekeeping system (instead of breaking down the sol into 25×53×67 or 25×67×53 SI second divisions) slows down clocks so that the 24-hour day is stretched to the length of that on Mars; Martian hours, minutes and seconds are thus 2.75% longer than their SI-compatible counterparts.[70][71]
TheDarian calendar is an arrangement of sols into a Martian year. It maintains a seven-sol week (retaining Sunday through Saturday naming customs), with four weeks to a month and 24 months to a Martian year, which contains 668 or 669 sols depending onleap years. The last Saturday of every six months is skipped over in the Darian calendar.
There are two diametrically opposed definitions of thedog year, primarily used to approximate the equivalent age ofdogs and other animals with similar life spans. Both are based upon apopular myth regarding theaging of dogs that states that a dog ages seven years in the time it takes a human to age one year.
In fact, the aging of a dog varies by breed (larger breeds tend to have shorter lifespans than small and medium-sized breeds); dogs also develop faster and have longer adulthoods relative to their total life span than humans. Most dogs are sexually mature by 1 year old, which corresponds to perhaps 13 years old in humans.[citation needed]Giant dog breeds andbulldogs tend to have the strongest linear correspondence to human aging, with longer adolescences and shorter overall lifespans; such breeds typically age about nine times as fast as humans throughout their lives.[74]
The galactic year, GY, is the time it takes theSolar System to revolve once around the galactic core, approximately 250 million years (megaannum or "Ma"). It is a convenient unit for long-term measurements. For example, oceans appeared on Earth after 4 GY, life is detectable at 5 GY, and multicellular organisms first appeared at 15 GY. Theage of the Earth is estimated at 20 GY.[75] This use of GY is not to be confused with Gyr forgigayear or Gy forGray (unit).
The Furman is a unit of angular measure equal to1⁄65,536 of a circle, or just under 20 arcseconds. It is named for Alan T. Furman, the American mathematician who adapted theCORDIC algorithm for 16-bit fixed-point arithmetic sometime around 1980.[76] 16 bits give a resolution of 216 = 65,536 distinct angles.
A related unit of angular measure equal to1⁄256 of a circle, represented by 8 bits, has found some use in machinery control where fine precision is not required, most notably crankshaft and camshaft position ininternal combustion engine controllers, and in video game programming. There is no consensus as to its name, but it has been called the 8-Bit Furman. These units are convenient because binary integer overflow resembles angular arithmetic: the value of an 8-bit integer overflows from 255 to 0 when a full circle has been traversed. This means binary addition and subtraction work as expected for angular arithmetic. Measures are often made using aGray code, which is trivially converted into more conventional notation. Its value is equivalent to about 0.0245 radians or 1.41°.
Mils andstrecks are small units of angle used by various military organizations for range estimation and translating map coordinates used for directing artillery fire.[77] The exact size varies between different organizations: there are 6400 NATO mils perturn (1 NATO mil = 0.982 mrad), or 6000 Warsaw pact mils per turn (1 Warsaw pact mil = 1.047 mrad). In the Swedish military, there are 6300 strecks per turn (1 streck = 0.997 mrad).
Coordinates were measured in grades on official French terrestrial ordnance charts from the French revolution well into the 20th century. 1 grade (or in modern symbology, 1 gon) = 0.9° or 0.01 right angle. One advantage of this measure is that the distance between latitude lines 0.01 gon apart at the equator is almost exactly 1 kilometre. It would be exactly 1 km if the original definition of 1 metre =1⁄10,000 quarter-meridian had been adhered to. One disadvantage is that common angles like 30° and 60° are expressed by fractional values (33+1⁄3 and66+2⁄3 respectively) so this "decimal" unit failed to displace the "sexagesimal" units equilateral-vertex – degree – minute – second invented by Babylonian astronomers.[neutrality isdisputed]
In 2011, theUnited States Environmental Protection Agency introduced thegallon gasoline equivalent as a unit of energy because their research showed most U.S. citizens do not understand the standard units. The gallon gasoline equivalent is defined as 33.7 kWh,[78] or about 1.213×108 joules.
Efficiency / fuel economy can be given asmiles per gallon gasoline equivalent.
The energy of various amounts of the explosiveTNT (kiloton, megaton, gigaton) is often used as a unit ofexplosion energy, and sometimes of asteroid impacts and violent explosive volcanic eruptions. One ton of TNT produces 4.184×109 joules, or (by arbitrary definition) exactly 109 thermochemical calories (approximately 3.964×106 BTU). This definition is only loosely based on the actual physical properties of TNT.
The energy released by theHiroshima bomb explosion (about 15 kt TNT equivalent, or 6×1013 J) is often used bygeologists as a unit when describing the energy ofearthquakes,volcanic eruptions, andasteroid impacts.
Prior to the detonation of the Hiroshima bomb, the size of theHalifax Explosion (about 3 kt TNT equivalent, or 1.26×1013 J), was the standard for this type of relative measurement. Each explosion had been the largest known artificial detonation to date.[79]
Aquad is a unit of energy equal to 1015 BTUs, or approximately 1.055×1018 J (slightly over one exajoule). It is suitably large to quantify energy usage by nations or by the planet as whole using everyday numbers. For example, in 2004, US energy consumption was about 100 Q/year, while demand worldwide was about 400 Q/year.[80]
Afoe is a unit of energy equal to 1044 joules (≈9.478×1040 BTU) that was invented by physicist Gerry Brown ofStony Brook University. To measure the staggeringly immense amount of energy produced by asupernova, specialists occasionally use the "foe", an acronym derived from the phrase [ten to the power of]fifty-oneergs, or 1051 ergs. This unit of measure is convenient because a supernova typically releases about one foe of observable energy in a very short period of time (which can be measured in seconds).
The rate at which heat is removed by melting one short ton (910 kg) of ice in 24 hours is called a ton of refrigeration, or even a ton of cooling. This unit of refrigeration capacity came from the days when large blocks of ice were used for cooling, and is still used to describe the heat-removal capabilities of refrigerators and chillers today. One ton of refrigeration is exactly equal to 12,000 BTU/h, or 3.517 kW.
With the phaseout of theincandescent lamp in the United States and European Union[globalize] in the early 21st century, manufacturers and sellers of more energy-efficient lamps have compared the visible light output of their lamps to commonly used incandescent lamp sizes with thewatt equivalent orwatt incandescent replacement (usually with a lowercase w as a unit symbol, as opposed to capital W for the actual wattage). 1 watt incandescent replacement corresponds to 15lumens. Thus, a 72-watthalogen lamp, a 23-wattcompact fluorescent lamp and a 14-wattlight-emitting diode lamp, all of which emit 1500 lumens of visible light, are all marketed as "100 watt incandescent replacement" (100w).
The volume of discharge of theAmazon River sometimes used to describe large volumes of water flow such as ocean currents. The unit is equivalent to 216,000 m3/s.[81]
Onesverdrup (Sv) is equal to 1,000,000 cubic metres per second (264,000,000 USgal/s). It is used almost exclusively inoceanography to measure the volumetric rate of transport ofocean currents.
TheBubnoff unit is defined as 1 micrometre per year (3.169×10−14 m/s), or one millimeter per 1,000 years. It is employed ingeology to measure rates of lowering of earth surfaces due toerosion.
Thelangley (symbol Ly) is used to measure solar radiation orinsolation. It is equal to one thermochemicalcalorie per square centimetre (4.184×104 J/m2 or ≈3.684 BTU/sq ft) and was named afterSamuel Pierpont Langley. Its symbol should not be confused with that for the light-year, ly.
One of the fewCGS units to see wider use, onestokes (symbol S or St) is a unit ofkinematicviscosity, defined as 1 cm2/s, i.e., 10−4 m2/s (≈1.08×10−3 sq ft/s).
AMERU (milli Earth rate unit) is a measure ofangular velocity equal to1⁄1000 of Earth'srotation rate: 1 MERU =7.292115×10^−8 radians per second or about 0.2625 milliradians/hour.[82] It was introduced by MIT's Instrumentation Laboratories (nowDraper Labs) to measure the performance ofinertial navigation systems.[83][84]
Inradio astronomy, the unit ofelectromagnetic flux is thejansky (symbol Jy), equivalent to 10−26 watts per square metre perhertz (= 10−26 kg/s2 in base units, about 8.8×10−31 BTU/ft2). It is named after the pioneering radio astronomerKarl Jansky. The brightest natural radio sources have flux densities of the order of one to one hundred jansky.
A material-dependent unit used innuclear andparticle physics and engineering to measure the thickness of shielding, for example around anuclear reactor,particle accelerator, orradiation or particle detector. 1 mwe of a material is the thickness of that material that provides the equivalent shielding of one metre (≈39.4 in) of water.
This unit is commonly used in underground science to express the extent to which theoverburden (usually rock) shields an underground space or laboratory fromcosmic rays. The actual thickness of overburden through which cosmic rays must traverse to reach the underground space varies as a function of direction due to the shape of the overburden, which may be a mountain, or a flat plain, or something more complex like a cliff side. To express the depth of an underground space in mwe (or kmwe for deep sites) as a single number, the convention is to use the depth beneath a flat overburden atsea level that gives the same overall cosmic raymuon flux in the underground location.
Thestrontium unit, formerly known as the Sunshine Unit (symbol S.U.), is a unit of biological contamination by radioactive substances (specificallystrontium-90). It is equal to onepicocurie of Sr-90 pergram of bodycalcium. Since about 2% of the human body mass is calcium, and Sr-90 has ahalf-life of 28.78 years, releasing 6.697+2.282 MeV per disintegration, this works out to about 1.065×10−12 grays per second. The permissible body burden was established at 1,000 S.U.
Bananas, like most organic material, naturally contain a certain amount of radioactive isotopes—even in the absence of any artificial pollution or contamination. Thebanana equivalent dose, defined as the additional dose a person will absorb from eating one banana, expresses the severity of exposure to radiation, such as resulting from nuclear weapons or medical procedures, in terms that would make sense to most people. This is approximately 78 nanosieverts – in informal publications one often sees this estimate rounded up to 0.1 μSv.
Natural background radiation typically increases with altitude above the earth's surface. Utilizing this phenomenon, dose resulting from radiological exposures can be expressed in units of flight-time.Flight-time equivalent dose is defined as the time spent in an aircraft at cruising altitude required to receive a radiological dose approximately equivalent to a radiological exposure such as a medicalx-ray. One hour of flight-time is approximately equivalent to a dose of 0.004 millisieverts.
In thepulp and paper industry,molar mass is traditionally measured with a method where theintrinsic viscosity (dL/g) of the pulp sample is measured in cupriethylenediamine (Cuen). The intrinsic viscosity [η] is related to the weight-average molar mass (indaltons) by theMark–Houwink equation: [η] = 0.070 Mw0.70.[85] However, it is typical to cite [η] values directly in dL/g, as the "viscosity" of the cellulose, confusingly as it is not a viscosity.
In measuring unsaturation in fatty acids, the traditional method is theiodine number. Iodine adds stoichiometrically to double bonds, so their amount is reported in grams of iodine spent per 100 grams of oil. The standard unit is a dimensionless stoichiometry ratio of moles double bonds to moles fatty acid. A similar quantity,bromine number, is used in gasoline analysis.
In pulp and paper industry, a similarkappa number is used to measure how muchbleaching a pulp requires.Potassium permanganate is added to react with the unsaturated compounds (lignin and uronic acids) in the pulp and back-titrated. Originally withchlorine bleaching the required quantity ofchlorine could be then calculated, although modern methods use multiple stages. Since the oxidizable compounds are not exclusively lignin and the partially pulped lignin does not have a single stoichiometry, the relation between the kappa number and the preciseamount of lignin is inexact.
Gas Mark is a temperature scale, predominantly found on Britishovens, that scaleslinearly with temperature above 135 °C (Gas Mark 1) and scales with thelog of Celsius below 135 °C.
Demography and quantitativeepidemiology arestatistical fields that deal withcounts or proportions of people, or rates of change in these.Counts and proportions are technicallydimensionless, and so have nounits of measurement, although identifiers such as "people", "births", "infections" and the like are used for clarity. Rates of change arecounts per unit of time and strictly have inverse time dimensions (per unit of time). Indemography and epidemiology expressions such as"deaths per year" are used to clarify what is being measured.
Prevalence, a common measure inepidemiology, is strictly a type ofdenominator data, a dimensionless ratio or proportion.Prevalence may be expressed as a fraction, a percentage or as the number of cases per 1,000, 10,000, or 100,000 in the population of interest.
A micromort is a unit ofrisk measuring a one-in-a-millionprobability ofdeath (frommicro- andmortality). Micromorts can be used to measure riskiness of various day-to-day activities. A microprobability is a one-in-a million chance of some event; thus a micromort is the microprobability of death. For example, smoking 1.4 cigarettes increases one's death risk by one micromort, as does traveling 370 km (230 miles) by car.
The large numbers of people involved indemography are often difficult to comprehend. A useful visualisation tool is the audience capacity of large sports stadiums (often about 100,000). Often the capacity of the largest stadium in a region serves as a unit for a large number of people. For example, Uruguay'sEstadio Centenario is often used inUruguay,[86][87] while in parts of the United States,Michigan Stadium is used in this manner.[88] In Australia, the capacity of theMelbourne Cricket Ground (about 100,000) is often cited in this manner. Hence theMelbourne Cricket Ground serves as both a measure of people and aunit of volume.[89][90][91]
The growth of computing has necessitated the creation of many new units, several of which are based on unusual foundations.
Volume or capacity of data is often compared to works of literature or large collections of writing. Popular units include the Bible, the Encyclopædia Britannica, phone books,the complete works of Shakespeare, and theLibrary of Congress.
When theCompact Disc began to be used as adata storage device as theCD-ROM, journalists often described the disc capacity (650 megabytes) by using the number of ChristianBibles that can be stored. TheKing James Version of the Bible in uncompressed plain 8-bit text contains about 4.5 million characters,[92] so aCD-ROM can store about 150 Bibles.
The print version of theEncyclopædia Britannica is another common data volume metric. It contains approximately 300 million characters,[93] so two copies would fit onto aCD-ROM and still have 50 megabytes (or about 11 bibles) left over.
The termLibrary of Congress is often used. It refers to the USLibrary of Congress. Information researchers have estimated that the entire print collections of the Library of Congress represent roughly 10 terabytes of uncompressedtextual data.[94]
A measure of quantity of data or information, the "nibble" (sometimes spelled "nybble" or "nybl") is normally equal to 4 bits, or one half of the common 8-bit byte. The nibble is used to describe the amount of memory used to store a digit of a number stored inbinary-coded decimal format, or to represent a single hexadecimal digit. Less commonly, 'nibble' may be used for any contiguous portion of a byte of specified length, e.g. "6-bit nibble"; this usage is most likely to be encountered in connection with a hardware architecture in which the word length is not a multiple of 8, such as older 36-bit minicomputers.
Incomputing, FLOPS (FLoating pointOperationsPerSecond) is a measure of a computer's computing power. It is also common to see measurements of kilo, mega, giga, and teraFLOPS.
It is also used to compare the performance of computers in practice.[95]
A measure to determine theCPU speed. It was invented byLinus Torvalds and is nowadays present on everyLinux operating system. However, it is not a meaningful measure to assess the actualCPU performance.
A computer programming expression, theK-LOC or KLOC, pronouncedkay-lok, standing for "kilo-lines of code", i.e., thousand lines of code. The unit was used, especially byIBM managers,[96] to express the amount of work required to develop a piece of software. Given that estimates of 20 lines of functional code per day per programmer were often used, it is apparent that 1 K-LOC could take one programmer as long as 50 working days, or 10 working weeks. This measure is no longer in widespread use because different computer languages require different numbers of lines to achieve the same result (occasionally the measure "assembly equivalent lines of code" is used, with appropriate conversion factors from the language actually used to assembly language).
Error rates in programming are also measured in "Errors per K-LOC", which is called thedefect density. NASA'sSATC is one of the few organizations to claim zero defects in a large (>500K-LOC) project, for the space shuttle software.
An alternative measurement was defined byPegasus Mail authorDavid Harris: the "WaP" is equivalent to 71,500 lines of program code, because that number of lines is the length of one edition ofLeo Tolstoy'sWar and Peace.[97]
The "tick" is the amount of time between timerinterrupts generated by the timer circuit of a CPU. The amount of time is processor-dependent.[98][99] The word "tick" is also used to describe steps of processing in apps and video games, for example, Minecraft servers process the simulation at a rate of 20 ticks per second,[100][better source needed] while other games commonly use tickrates of 30, 60, 64, or 128 ticks per second.
In genetics, acentimorgan (abbreviated cM) or map unit (m.u.) is a unit for measuring genetic linkage. It is defined as the distance between chromosome positions (also termed loci or markers) for which the expected average number of intervening chromosomal crossovers in a single generation is 0.01. It is often used to infer distance along a chromosome. One centimorgan corresponds to about 1 million base pairs in humans on average.
Chess software frequently uses centipawns internally or externally as a unit measuring how strong each player's situation position is, and hence also by how much one player is beating the other, and how strong a possible move is.[101] 100 centipawns =the value of 1 pawn – more specifically, something like the average value of the pawns at the start of the game, as the actual value of pawns depends on their position. Loss of a pawn will therefore typically lose that player 100 centipawns. The centipawn is often used for comparing possible moves, as in a given position, chess software will often rate the better of two moves within a few centipawns of each other.
The garn is NASA's unit of measure for symptoms resulting fromspace adaptation syndrome, the response of the human body to weightlessness in space, named after US SenatorJake Garn, who became exceptionally spacesick during an orbital flight in 1985. If an astronaut is completely incapacitated by space adaptation syndrome, he or she is under the effect of one garn of symptoms.[102]
Formerly used in real estate transactions in the American Southwest, it was the number of pregnant cows an acre of a given plot of land could support. It acted as a proxy for the agricultural quality, natural resource availability, and arability of a parcel of land.[103]
Numbers very close to, but below one are often expressed in "nines" (N – not to be confused with the unitnewton), that is in the number of nines following the decimal separator in writing the number in question. For example, "three nines" or "3N" indicates 0.999 or 99.9%, "four nines five" or "4N5" is the expression for the number 0.99995 or 99.995%.[104][105][106]
Typical areas of usage are:
The dol (from theLatin word for pain,dolor) is aunit of measurement forpain.James D. Hardy,Herbert G. Wolff, andHelen Goodell ofCornell University proposed the unit based on their studies of pain during the 1940s and 1950s. They defined one dol to equal ajust-noticeable difference in pain. The unit never came into widespread use and other methods are now used to assess the level of pain experienced by patients.
The Schmidt sting pain index and Starr sting pain index arepain scales rating the relative pain caused by differenthymenoptera stings. Schmidt has refined hispain index (with a 1–4 scale) with extensive anecdotal experience, culminating in a paper published in 1990 which classifies the stings of 78 species and 41 genera ofHymenoptera. TheStarr sting pain scale uses the same 1–4 scale.
The ASTA (American Spice Trade Association)pungency unit is based on a scientific method of measuring chili pepper "heat". The technique utilizeshigh-performance liquid chromatography to identify and measure the concentrations of the various compounds that produce a heat sensation. Scoville units are roughly1⁄15 the size of pungency units while measuringcapsaicin, so a rough conversion is to multiply pungency by 15 to obtain Scoville heat units.[107]
TheScoville scale is a measure of the hotness of achili pepper. It is the degree of dilution in sugar water of a specific chili pepper extract when a panel of 5 tasters can no longer detect its "heat".[108] Purecapsaicin (the chemical responsible for the "heat") has 16 million Scoville heat units.
Up to the 20th century, alcoholic spirits were assessed in the UK by mixing with gunpowder and testing the mixture to see whether it would still burn; spirit that just passed the test was said to be at 100° proof. The UK now uses percentagealcohol by volume (ABV) at 20 °C (68.0 °F), where spirit at 100° proof is approximately 57.15% ABV. In the US, "proof number" is defined as twice the ABV at 60 °F (15.6 °C).[109]
Thesavart is an 18th-century unit for measuring the frequency ratio of two sounds. It is equal to1⁄1000 of adecade (not to be confused with the time period equal to 10 years). Thecent is preferred for musical use.
The erlang, named after A. K. Erlang, as adimensionless unit is used intelephony as a statistical measure of the offered intensity oftelecommunicationstraffic on a group of resources. Traffic of one erlang refers to a singleresource being in continuous use, or twochannels being at fifty percent use, and so on,pro rata. Much telecommunications management and forecasting software uses this.
The crab is defined as the intensity of X-rays emitted from theCrab Nebula at a given photon energy up to 30kiloelectronvolts. The Crab Nebula is often used for calibration of X-ray telescopes. For measuring the X-ray intensity of a less energetic source, the milliCrab (mCrab) may be used.
One crab is approximately 24 pW/m2.
Maps, architecture and prop models use a scale of 1 foot = 16 units.
Measurements are in metric feet (30cm)...
The land is not let by the acre, but by what is termed a "cow's grass" — so many "cows' grass" to a farm. A "cow's grass" is a measure of land; usually it means as much mountain grazing-land as will keep a cow during the summer, and as much arable-land as will keep the cow-house in fodder during the winter.