List of unusual units of measurement

List of unusual units of measurement
For units of measure primarily used in countries where English is not the main language, see the article specific to that country, a list of which can be found in the systems of measurement article.

An unusual unit of measurement is a unit of measurement that does not form part of a coherent system of measurement; especially in that its exact quantity may not be well known or that it may be an inconvenient multiple or fraction of base units in such systems. This definition is deliberately not exact since it might seem to encompass units such as the week or the light-year which are quite "usual", in the sense they are often used; if they are used out of context they may be "unusual", as demonstrated by the FFF system of units.

Unusual units of measure are sometimes used by scientists, especially physicists and mathematicians, and other technicians, engineers and computer programmers, either humorously or for real convenience when dealing with objects in the real world whose quantities in more conventional units may be awkward to use. They are also employed by journalists in an attempt to give meaningful comparisons. Whether such comparisons actually are meaningful is open to debate, since the comparative quantity itself may not be well known with much accuracy.[citation needed]


Systems of measurement

MTS units

During the twentieth century, the Soviets and French briefly used a variant of the metric system where the base unit of mass was the tonne.

FFF units

Unit Dimension Definition SI Value
furlong length 660 ft 201.168 m
firkin[1] mass 90 lb 40.8233 kg
fortnight time 14 days 1,209,600 s

Most countries use the International System of Units (SI). In contrast, the Furlong/Firkin/Fortnight system of units of measurement draws its attention by being extremely old fashioned, and off-beat at the same time.[2]

One furlong per fortnight is very nearly 1 centimetre per minute (to within 1 part in 400). Indeed, if the inch were defined as 2.54 cm rather than 2.54 cm exactly, it would be 1 cm/min. Besides having the meaning of "any obscure unit", furlongs per fortnight have also served frequently in the classroom as an example on how to reduce a unit's fraction. The speed of light may be expressed as being roughly 1.8 terafurlongs per fortnight.[3][4]

SI-imperial hybrids

In the US, mongrel units are sometimes formed by a combination of traditional units, which are widely used, and metric units. Thus, "grams per fluid ounce" and "grams per pound of body weight" are common units used in sports nutrition, for example, to express the concentration of carbohydrate in a beverage.

A hybrid standard quantity used in mining is the assay ton (AT), which is as many milligrams as there are troy ounces in a ton: 29.17 grams if the ton used is the short ton, and 32.67 g if the ton used is the long ton. So to find how many ounces of gold are in a ton of rock, one measures the number of milligrams of gold in an assay ton of rock.

There are also reports of engineers using base-ten SI prefixes in combination with Imperial or US customary units, for example the kiloyard (914.4 m). The kip or kilopound is regularly used in structural engineering. Similarly, the kilofoot is quite common in US telecommunication engineering, as significant distances in cable route planning are usually given in thousands of feet. Instruments like optical time-domain reflectometers usually have an option to display results in kilofeet. Perhaps most common is the use of the thou or mil, defined as 1/1,000 of an inch (25.4 µm), frequently used in the manufacturing industry and to measure the thickness of very thin materials like film and plastic sheeting. A related unit is the circular mil, used for measuring the cross-sectional area of wire.

In the UK, it is still (2007) not uncommon to find the "metric foot" in use in the domestic refurbishment market. A metric foot is 30 cm and usually it is used with lumber (timber in the UK) that is only available in metric yards or 90 cm multiples (see metric inch below). Its square form is also common in some fields: for example, carpet and other flooring materials, when supplied in "tiles" (squares), are often supplied in this size.

In commercial office fitout in the UK, most suspended ceilings and raised floors are based on a 60 cm module, or 2 "metric feet".

A useful unit when working with optical pathway lengths in the lab is the one foot per nanosecond approximation for the speed of light. In electronic circuitry, where the velocity of propagation is somewhat slower than the speed of light in a vacuum, similar approximations can be used for "signal races" in the circuitry. (See light-nanosecond below.)

Derived units

There are some obscure metric units: with arbitrary units and prefixes, a common unit can be expressed with an unfamiliar term. Among physicists there is the in-joke replacing common units with uncommon units, as in velocity: metres per second is equivalent to hertz per dioptre (Hz/dpt). In this case, the reciprocal values of metre and second — dioptre and hertz, respectively — are used to contrive the same unit. The becquerel could also be used instead of hertz, as it is a measure of aperiodic events per time, instead of the periodic events per time measured by the hertz.



Parsecs are used in astronomy to measure enormous interstellar distances. A parsec is approximately 3.26 light-years or about 3.085×1016 m (1.917×1013 mi). Combining it with the "atto-" prefix yields attoparsec (apc), a conveniently human-scaled unit of about 3.085 centimetres (1.215 in) that has no obvious practical use. 1 attoparsec/microfortnight is nearly 1 inch/second.[5]


The light-nanosecond was popularized as a unit of distance by Grace Hopper as the distance which a photon could travel in one billionth of a second (roughly 30 cm or one foot): "The speed of light is one foot per nanosecond."[6] In her speaking engagements, she was well-known for passing out light-nanoseconds of wire to the audience, and contrasting it with light-microseconds (a coil of wire 1,000 times as long) and light-picoseconds (the size of ground black pepper). Over the course of her life, she had many motivations for this visual aid, including demonstrating the waste of sub-optimal programming, illustrating advances in computer speed, and simply giving young scientists and policy makers the ability to conceptualize the magnitude of very large and small numbers.[7]

Metric inch

The international inch is defined to be exactly 25.4 mm. It is approximated to 25 mm as a "metric inch".

A metric inch was used in some Soviet computers when Soviet engineers built unlicensed copies based on blueprints drawn in the US.[citation needed] Clones existed of many machines such as PDPs and early IBM PCs. The computers would look like machines made in the US, but some of the components, mainly those using longer slots or more pins, were not interchangeable due to the non-interoperable nature of the metric inch. Shorter-slotted or lower pin count original hardware was often forced in by hand if needed, as such measurement discrepancies were within tolerance; longer chips, boards, and cables, with differences that would mismatch contacts, required converters, often home-made. Because microelectronics were rare and prohibitively expensive in the Soviet Union, computers cobbled together or upgraded with mismatched original, custom-built, and cloned components, more than just common, were the norm.

The similarly derived metric foot (300 mm) was once used in the United Kingdom for some expensive materials. It was also briefly the unit used in the trade of timber when neither feet nor metres were used.[citation needed]


In vehicle driving tests in the UK and elsewhere, braking distances can be given in metres or in car lengths (with a car for this purpose being typically around 4 m long). A "car length" or "length" is also a common unit for estimating the distance between two cars in auto racing.


In Britain, newspapers and other media will frequently refer to lengths in comparison to the length (8.4 m/27.6 ft) or height (4.4 m/14.4 ft) of a London Routemaster double-decker bus.

The UK Department of Transport has changed the definition of the maximum acceptable length dimensions about 40 times since 1900, as suggested by the UK documentary "100 Years of British Buses" (1996).[citation needed]

Similarly, in the United States the yellow schoolbus is a common point of comparison, with an average length of around 35 feet (11 m) .

Popular topics for such comparison include the blue whale (30 m), the IMAX screen (22 × 16.1 m), and the diplodocus (35 m).[8]

Football field (length)

The length of an American football field is 100 yd (91 m). If the end zones are included, it is 120 yd (110 m), but 100 yards is used informally as a unit, to allow easier conversion from formal measurement in feet or yards. It describes the size of a large building or a park, a distance which is not too short, but which one can walk over.

The Canadian football field is 65 yards (59 m) wide and 110 yards (100 m) long with end zones 20 yards (18 m) deep.

Media in the UK also use the football pitch as a unit of length, although an area of the Association football (soccer) pitch is not fixed, but varies within a limit of 90–120 m (98–130 yd) in length and 45–90 m (50–100 yd) in width. The usual size of a football pitch is 105 m × 68 m (115 yd × 75 yd), the area used for matches in the UEFA Champions League.

Other codes of football, known in various parts of the world, use football fields with different sizes and shapes, and may be used as a similar reference.[citation needed]

Tall buildings

In the US, buildings such as the Empire State Building (449 m or 1,473 ft), Willis Tower (519 m or 1,703 ft), and Seattle Space Needle (184 m/604 ft) are used as comparative measurements of height, as are the Statue of Liberty and Washington Monument. The Empire State Building (but not the others mentioned) is also used in Britain for describing particularly large/tall objects.

In France, the Eiffel Tower (324 m or 1,063 ft), and the UK, Nelson's Column (185 ft or 56 m), Blackpool Tower (158 m or 518 ft), the Tower of London (96.3 m or 316 ft), and St Paul's Cathedral (354 ft or 108 m) are commonly used by British newspapers or reference books to give the comparative heights of buildings or, occasionally, mountains.

In 2006, upon completion of a full restoration, Nelson's Column was found to be 16 ft or 4.9 m shorter than previously supposed. Nelson's Column is now considered 169 ft 3 in (51.59 metres) tall from the bottom of the pedestal to the top of Nelson's hat. This measurement has been obtained by laser survey.[9] This could introduce some uncertainty into future use of this unit as a reference.

In Canada (and occasionally elsewhere), the Toronto CN Tower (553 m or 1,814 ft) is used as a unit of length.[10][11]


A city block (in most US cities) is between 1/16 and 1/8 mi (100 and 200 m). In Manhattan, the measurement "block" usually refers to a north-south block, which is 1/20 mi (80 m). 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 the Manhattan Metric).

Circle of the Earth

The circumference of a great circle of the Earth (about 40,000 km/25,000 mi/21,600 nmi/199,000 furlongs) is often compared to large distances. For example, one might say that a large number of objects laid end-to-end at the equator "would circle the Earth four and a half times".[12] According to WGS-84, the circumference of a circle through the poles (twice the length of a meridian) is 40,007,862.917 metres (131,259,392.772 ft) and the length of the equator is 40,075,016.686 m (131,479,713.537 ft). Despite the fact that the difference (0.17%) between the two is insignificant at the low precision that these quantities are typically given to, it is nevertheless often specified as being at the equator.[citation needed]

Both the nautical mile and the kilometre are derived from the circle of the earth. This is taken as a circle, and a minute of the earth becomes the nautical mile (360 degrees of 60 minutes), and the kilometre (400 degrees of 100 minutes).

Earth-to-Moon distance

The distance from the Earth to the Moon (about 380,000 km [about 240,000 miles] on average, if measured from the Earth's surface to the moon's surface) is sometimes used in the same circumstances as the Circle of the Earth unit is used above. For example, one might say that a large number of objects laid end-to-end "would reach all the way to the Moon and back two-and-a-half times."


The siriometer is a rarely used astronomical measure equal to one million astronomical units, i.e., one million times the average distance between the Sun and Earth. 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 star Sirius.



One barn is 10−28 square meters, about the cross-sectional area of a uranium nucleus. The name probably derives from early neutron-deflection experiments, in which the uranium nucleus was described, comparatively, as being "big as a barn". Additional units include the microbarn (or "outhouse")[13] and the yoctobarn (or "shed")[14][15].


The nanoacre is a unit of real estate on a VLSI chip equal to 0.00627264 sq in (4.0468564224 mm2) or the area of a square of side length 0.0792 in (2.01168 mm). "The term gets its humor from the fact that VLSI nanoacres have costs in the same range as real acres in Silicon Valley once one figures in design and fabrication-setup costs."[16]


The square is an Imperial unit of area that is used in the construction industry in North America,[17] and was historically used in Australia by real estate agents. One square is equal to 100 square feet. A roof's area may be calculated in square feet, then converted to squares, which can then be used to order roofing materials by the square.

Football field (area)

In many countries,[citation needed] an Association football pitch, or field, is used as a man-in-the-street unit of area.[18][19] It is necessarily restricted to order of magnitude comparisons by the fact that football pitches are officially allowed to measure between 100 and 110 m in length, and between 64 and 75 m in width; i.e. between 0.64 and 0.83 ha (1.6–2 ac).[20]

An American football field, including both end zones, is 360 ft by 160 ft (ca. 110 x 49 m), or 57,600 square-feet (5,350 m², 0.54 ha, 1.32 acres). A Canadian football field is 65 yards wide and 110 yards long (ca. 101 x 59 m) with end zones adding a combined 40 yards to the length, making it 64,350 square-feet (5,980  m², 0.60 ha, 1.477 acres)

An Australian rules football field may be approximately 150 metres (or more) long goal to goal and 135 metres (or more) wide, making it a considerably bigger area.

Various countries, regions, and cities

Wales (red) in the UK (pink)

The area of a familiar country, state or city is often used as a unit of measure, especially in journalism.


Equal to 20,779 km² (8,023 sq mi), the country of Wales is used in phrases such as "an area the size of Wales" or "twice the area of Wales".[21][22] England is 6.275 times the size of Wales, and Scotland is roughly four times the size of Wales. Ireland is four times larger than Wales, and France is about twenty-five times larger.

The British comedy show The Eleven O'Clock Show parodied the use of this measurement, by introducing a news article about an earthquake in Wales, stating that an area the size of Wales was affected. The Radio 4 program More or Less introduced the idea of "kiloWales" - an area 1000 times the size of Wales. The Register introduced the nanoWales (20.78 m2).


In the United States, the areas of Rhode Island (1,545 sq mi/4,000 km2), the smallest state, Texas (268,601 sq mi/695,670 km2) and, less commonly, Alaska (656,425 sq mi/1,700,130 km2) are used in a similar fashion. Antarctica's Larsen B ice shelf was approximately the size of Rhode Island until it broke up in 2002. Due to Rhode Island being a relatively small unit of measurement (and, perhaps, due to its area being 33% water), many comparisons to the size of Rhode Island are somewhat imprecise.[23] The US Central Intelligence Agency uses Washington, D.C. (61.4 sq mi/159 km2) as a comparison for city-sized objects.[citation needed]

Almost any state will be used in this fashion to describe the area of another country.

Other countries

In Canada, the standard unit of comparison is often Prince Edward Island (5,683 km2/2,194 sq mi),[24] the smallest Canadian province.

In Russia, France (551,695 km2/213,011 sq mi) is often used as a comparison for regions of Siberia.[25] This was so popular in the Soviet era that the phrase "как две Франции" (twice the size of France) became a stock phrase to denote any large area.

The country of Belgium (30,528 km2/11,787 sq mi) has also often been used when comparing areas, to the point where it has been regarded as a meme[26] and where there is a website dedicated to notable areas which have been compared to that of Belgium.

The Isle of Wight (380 km² or 147 sq mi), an island off the south coast of mainland England, is commonly used to define smaller areas.


Board foot or super foot

A board foot is an American unit of volume, used for wood. It is equivalent to 1 inch × 1 foot × 1 foot (144 cu in/2,360 cm3). However, in practice, it is defined differently for hardwood and softwood. It is also found in the unit of density pounds per board foot. In Australia and New Zealand the terms super foot or superficial foot were formerly used for this unit.

Hoppus foot

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. Following the so-called "quarter-girth formula" (the square of one quarter of the circumference in inches multiplied by one 144th 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. The hoppus board foot, when milled, yields a board foot. The volume yielded by the quarter-girth formula is 78.5% of cubic measure.[27]


The stere (st) is equal to a cubic metre or kilolitre. It is used for firewood, the measure being for the normal stack (including holes).


The Hubble-Barn is a humorous unit of volume, equal to 13.1 L (3.45 gallons)[28]. It is arrived at by multiplying an incredibly small unit of area, the Barn, which is on the scale of the area of an atomic nucleus at 100 square femtometers, with an incredibly large unit of length, the length of the observable universe, given by the speed of light divided by the hubble parameter, or 1 X 1026 m. The humor of the Hubble-Barn lies in the fact that a straw with such extreme individual dimensions, an area of an atomic nucleus, as long as the observable universe, has a terrestrially familiar volume.

Olympic-size swimming pool

For larger volumes of liquid, one measure commonly used in the media in many countries is the Olympic-size swimming pool.[29] A large Olympic swimming pool with dimensions 50 m × 25 m × 2 m (approx 164 ft × 82 ft × 6.6 ft) holds 2500 m³ – about 2 acre-feet, 660,000 gallons, or 1/200,000 of a sydharb.

Sydney Harbour

A unit of volume used in Australia for water. One Sydney Harbour, also called a Sydharb (or sydarb), is the amount of water in Sydney Harbour: 400,000 acre-feet, or approximately 500 gigalitres.[30]

Melbourne Cricket Ground

Australia's largest and best known sports stadium, the Melbourne Cricket Ground or MCG is used there as a unit of volume.[31][32]

Royal Albert Hall

The Royal Albert Hall, a large concert hall, is sometimes used as unit of volume in the UK, particularly when referring to volumes of rubbish placed in landfill.[33] The volume of the auditorium is between 3 and 3.5 million cubic feet (between 85,000 and 99,000 cubic metres).[34]



In 1793, the French term "grave" (from "gravity") was suggested as the base unit of mass for the metric system. In 1795, however, due in no small part to the French Revolution, the name "kilogram" was adopted instead.[35]

Bag of sugar

The mass of a bag of sugar (typically 500 grams) has become used as a quasi-standard for household objects,[36] so that something may weigh "as much as 3 bags of sugar".

Bag of cement

The mass of an old bag of cement was one hundredweight ~ 112lb, approximately 50 kg.[citation needed] The amount of material that, say, an aircraft could carry into the air is often visualised as the number of bags of cement that it could lift.[citation needed] In the concrete and petroleum industry, however, a bag of cement is defined as 94 pounds (~ 42.6 kg), because it has an apparent volume close to 1 cubic foot.[37]


The weight of an elephant, sometimes more specifically "the weight of an African bull elephant" (about 6 tons), is sometimes used by palaeontologists as a unit of weight when describing the weight of large dinosaurs[38] or other extinct creatures, such as Indricotherium.

Fully loaded 747

The maximum takeoff weight of most earlier models of the Boeing 747 is 800,000 pounds, or 360 tonnes. In the media, multiples of this mass can be used to describe very heavy objects, e.g. "It weighs as much as five fully loaded 747s."[citation needed]


When reporting on the masses of extrasolar planets, astronomers often discuss them in terms of multiples of Jupiter's mass (1.9 ×1027 kg).[39] 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 the Milky Way weighs ~6 ×1011 M.

Solar mass also has a special use when estimating orbital periods and distances of 2 bodies using Kepler's laws: a3 = MtotalT2, where a is length of semi-major axis in AU, T is orbital period in years and Mtotal is the combined mass of objects in M. 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 to Mtotal ~ 1, a ~ 1 and T ~ 1.



In nuclear engineering and astrophysics contexts, the shake is sometimes used as a conveniently short period of time. 1 shake is defined as 10 nanoseconds.[40]


In computing, the jiffy is the duration of one tick of the system timer interrupt. Typically, this time is 0.01 seconds, though in some earlier systems (such as the Commodore 8-bit machines) the jiffy was defined as 1/60 of a second, roughly equal to the vertical refresh period (i.e. the field rate) on NTSC video hardware (and the period of AC electric power in North America).


One unit derived from the FFF system of units is the microfortnight, one millionth of the fundamental time unit of FFF, which equals 1.2096 seconds. This is a fairly representative example of "hacker humor",[41] and is occasionally used in operating systems; for example, the OpenVMS TIMEPROMPTWAIT parameter is measured in microfortnights.[42]

Decimalisations of time

The measurement of time is unique in SI in that while the second is the base unit, and measurements of time smaller than a second use prefixed units smaller than a second (e.g. microsecond, nanosecond, etc.), measurements larger than a second instead use traditional divisions, including the sexagesimal-based minute and hour as well as the less regular day and year units. SI allows for the use of larger prefixed units based on the second, a system known as metric time, but this is unusual.

There have been numerous proposals and usage of decimal time, most of which were based on the day as the base unit. For instance, in dynastic China, the was a unit that represented 1/100 of a day. (It has since been refined to 1/96 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 each divided into 100 seconds. Ordinal dates and Julian dates allow for the expression of a decimal portion of the day.[43] Decimal time proposals are frequently used in fiction, often in futuristic works.

In addition to decimal time, there also exist binary clocks and hexadecimal time.

Dog year

A unit of measurement equal to one seventh of a year, or approximately 52 days, is primarily used to approximate the equivalent age of dogs and other animals with similar life spans. It is based upon a popular myth regarding the aging 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; dogs also develop faster and have longer adulthoods relative to their total life span than humans.) While the typical convention is to identify the "dog year" as the shorter length of time than the standard "human year" (thus, a 12-year-old dog is said to be 84 "in dog years"),[44] it is also not unheard of to have the 52-day unit be identified as a "human year" and the full 365-day year as a "dog year." When the unit is used, measurements in both "dog years" and "human years" are generally included together, to more clearly indicate which name is used for each unit.[44]

Galactic year

The most common large-scale time scale is millions of years (Megaannum or Ma). However, for long-term measurements, this still requires rather large numbers. Using as a measure the time it takes for the solar system to revolve once around the galactic core (GY - not to be confused with Gyr for Gigayear), approximately 250 Ma, yields some easily memorizable numbers. In this scale, oceans appeared on Earth after 4 GY, life began at 5 GY, and multicellular organisms first appeared at 15 GY. Dinosaurs went extinct about 1/4 GY ago, and the true age of mammals began about 0.2 GY ago. The age of the Earth is estimated at about 20 GY.[45] Therefore a 25-year-old person is 1 x 10-7GY or 0.1µGY.

Angular measure


The Furman is a unit of angular measure equal to 1⁄65,536 of a circle. It is named for Alan T. Furman, the American mathematician who adapted the CORDIC algorithm for 16-bit fixed-point arithmetic sometime around 1980.[46] 16 bits give a resolution of 216 = 65536 distinct angles.

Binary degree, binary radian, brad

A related unit of angular measure equal to 1⁄256 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 in internal combustion engine controllers, but there is no consensus as to its name. This unit is also used in video game programming. These units are convenient because they form cycles: for the 8-bit unit, the value overflows from 255 to 0 when a full circle has been traversed. Measures are often made using a Gray code, which is trivially converted into more conventional notation.

Angular mil

The angular mil is used by many military organisations to measure plane angle and so to triangulate distances, given an object's apparent and actual size. It is approximately the angle which has a tangent of 1/1000; in NATO standard, this is rounded to 1⁄6400 of a circle, although other definitions are in use. Its name derives from Latin: millesimus ("thousandth") and so the fact it is used mostly by the military is coincidental to its name.[47]


Tons of TNT

The explosive energy of various amounts of the explosive TNT (kiloton, megaton, gigaton) is often used as a unit of explosion energy, and sometimes of asteroid impacts and violent explosive volcanic eruptions. One ton of TNT is 4.184 × 109 joules, or 109 thermochemical calories (≈3.964 × 106 BTU). This definition is not based on the actual physical properties of TNT.

Hiroshima bomb

The energy released by the Hiroshima bomb explosion (about 15 kT TNT equivalent, or 6 x 1013 J) is often used by geologists as a unit when describing the energy of earthquakes, volcanic eruptions and asteroid impacts.


A foe is a unit of energy equal to 1044 joules (≈9.478 × 1040 BTU) that was coined by physicist Gerry Brown of Stony Brook University. To measure the staggeringly immense amount of energy produced by a supernova, specialists occasionally use the "foe", an acronym derived from the phrase [ten to the power of] fifty-one ergs, 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).

Other metric-compatible scales


It is common in particle physics, where mass and energy are often interchanged, to use eV/c2, where c is the speed of light in a vacuum (from E = mc2). Even more common is to use a system of natural units with c set to 1, and simply use eV as a unit of mass.

1 amu = 931.46 MeV/c2

Langley: energy intensity

The langley (symbol Ly) is used to measure solar radiation or insolation. It is equal to one thermochemical calorie per square centimetre (4.184×104 J/m² or ≈3.684 BTU/sq ft) and was named after Samuel Pierpont Langley.

Stokes: kinematic viscosity

One of the few CGS units to see wider use, one stokes (symbol S or St) is a unit of kinematic viscosity, defined as 1 cm²/s, i.e., 10−4 m²/s (≈1.08×10−3 sq ft/s).

Jansky: electromagnetic flux

In radio astronomy, the unit of electromagnetic flux is the jansky (symbol Jy), equivalent to 10−26 watts per square metre per hertz (= 10−26 kg/s2 in base units, about 8.8×10−31 BTU/ft2). It is named after the pioneering radio astronomer Karl Jansky. The brightest natural radio sources have flux densities of the order of one to one hundred jansky.

Metre of water equivalence

A material-dependent unit used in nuclear and particle physics and engineering to measure the thickness of shielding, for example around a nuclear reactor, particle accelerator, or radiation 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 the overburden (usually rock) shields an underground space or laboratory from cosmic 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 at sea level that gives the same overall cosmic ray muon flux in the underground location.

Dietary intake

Dietary intake of energy, or of various nutrients, is usually expressed as a quantity per day, rather than per second. Sometimes body mass is factored in.

An intake of 2500 kilocalories per day is about 121 watts. This gives the average power of the body, dissipated over 24 hours in heat and mechanical energy.

An intake of 0.5 gram of protein per day and per kilogram of body weight is about 5.79 10−9 s−1, the reciprocal of 172,800,000 seconds or 2000 days. This means it would take you 2000 days to eat your weight of protein.

Strontium unit: radiation dose

The strontium unit, formerly known as the Sunshine Unit (symbol S.U.), is a unit of biological contamination by radioactive substances (specifically strontium-90). It is equal to one picocurie of Sr-90 per gram of body calcium. Since about 2% of the human body mass is calcium, and Sr-90 has a half-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.

Banana equivalent dose

Bananas, like most organic material, naturally contain a certain amount of radioactive isotopes—even in the absence of any artificial pollution or contamination. The banana 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.


Encyclopaediae, Bibles, and the Library of Congress: data storage capacities

When the Compact Disc began to be used as a data storage device, the CD-ROM, journalists had to compare the disc capacity (650 MB) to something everyone could imagine. Since many Western households have a Christian Bible, and the Bible is a comparatively long book, it was often chosen for this purpose. The King James Version of the Bible in uncompressed plain 8-bit text contains about 4.5 million characters,[48] so a CD-ROM can store about 150 Bibles.

The Encyclopædia Britannica is another common data size metric — it contains approximately 300 million characters,[citation needed] so two copies would fit comfortably onto a CD-ROM.

The term Library of Congress is sometimes used as a unit of measurement when discussing large amounts of data. It refers to the US Library of Congress. One Library of Congress is used as approximately 20 tebibytes of uncompressed textual data,[49][50] or 10 terabytes according to other uses.[51][52]

In most cases, diagrams and photographs are not included in the total — since these take considerably more space than text, this would be an important consideration for practical storage of large book collections. In practice, diagrams can often be expressed more compactly using vector graphics, and data compression software can pack more text into the available space. It is possible to compress English text to about 11% of its original size.[53] Thus one might claim that the entire Library of Congress could be packed onto a single 2.2 terabyte storage unit — excluding the pictures. Furthermore, the modern Britannica contains over 1000 audio and video clips,[54] taking the size beyond that of a CD, meaning that a DVD-ROM is required.

A similar unit of measure for early computers was phone numbers and phone books.

Quantity of alcohol

In various countries, a unit of alcohol or standard drink is defined to measure the amount of alcohol consumed. It is usually a specified number of grams or millitres of alcohol. For instance, in the UK a unit of alcohol is 10 mL (7.9 g, 0.34 fl oz US or 0.35 fl oz imperial, 0.28 oz), so a UK pint (568 mL) of 5%ABV ale contains about 2.8 units (0.568 × 5 = 2.84).

In the United States, a "drink" usually refers to the amount of alcohol required to raise one's blood alcohol content by .01%. The benchmarks of this measurement are usually a 12-ounce can of beer, a 5½-ounce glass of wine, or a 1½-ounce shot of hard liquor. Unlike the UK, the measurement is not exact, due to differences in the way alcohol is metabolized by different people and variations in the amount of alcohol in drinks. The "drink" unit is widely taught in American high schools.[citation needed]

In Finland, larger quantities of alcohol are often visualized with the standard Koskenkorva bottle (0.5 l of 38%).


The thickness of a human finger is an informal measure of depth of fluid, and thus (indirectly) of the volume of a drink in a given glass.


The Stoddard is a measurement used by political campaigns to determine the density of a canvassing area. It is measured in doors per acre.

Sagan: scalar

A whimsical unit of measure equalling at least 4,000,000,000. Based on the quote "billions of stars" used by Carl Sagan and popularized with the derivation "billions and billions of stars" by Johnny Carson.

Big Mac Index: purchasing power parity

The Economist's Big Mac Index compares the purchasing power parity of countries in terms of the cost of a Big Mac hamburger.[55] This was felt to be[citation needed] a good measure of the prices of a basket of commodities in the local economy including labour, rent, meat, bread, cardboard, advertising, lettuce, etc.

A similar system used in the UK is the 'Mars bar'. Tables of prices in Mars Bars have intermittently appeared in newspapers over the last 20 years, usually to illustrate changes in wages or prices over time without the confusion caused by inflation.[56]


The Garn is NASA's unit of measure for symptoms resulting from space adaptation syndrome, the response of the human body to weightlessness in space, named after US Senator Jake 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.[57]

Inverse femtobarn

An inverse femtobarn is a measurement of particle collision events per femtobarn.

KLOC: computer program length

A computer programming expression, the K-LOC or KLOC, pronounced kay-lok, standing for "kilo-Lines of Code", i.e., thousand lines of code. The unit is used, especially by IBM managers,[58] 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.

Error rates in programming are also measured in "Errors per K-LOC", which is called the defect density. NASA's SATC is one of the few organisations to claim zero defects in a large (>500K-LOC) project, for the space shuttle software.


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 in binary-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 world length is not a multiple of 8, such as older 36-bit minicomputers.


In computing, FLOPS (FLoating point Operations Per Second) is a measure of a computer's computing power. It is also common to see measurements of kilo-, mega-, and teraFLOPS.

It is also used to compare the performance of algorithms in practice.[citation needed]


Numbers very close to, but below one are often expressed in nines (N - not to be confused with the unit newton), 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%.[citation needed]

Typical areas of usage are:

  • the reliability of computer systems, that is the ratio of uptime to the sum of uptime and downtime. "Five nines" reliability in a continuously operated system means an average downtime of no more than approximately five minutes per year.
  • the purity of materials, such as gases and metals.

Proof: alcohol concentration

Up to the 20th century, alcoholic spirits were assessed in the UK by mixing with gunpowder and testing the mixture to see if it would still burn; spirit that just passed the test was said to be at 100° proof. The UK now uses percentage alcohol by volume at 20 °C (68 °F), where spirit at 100° proof is approximately 57.15% ABV; the US uses a proof number of twice the ABV at 60 °F (15.5 °C).[citation needed]

Savart: audible frequency ratio

An 18th century unit for measuring the frequency ratio of two sounds, it is equal to 1/300 of an octave, or 1/25 of a semitone. Still used in some programs, but considered too rough for most purposes. Cent is preferred.

Scoville heat unit: pepper hotness

The Scoville scale is a measure of the hotness of a chili 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'.[59] Pure capsaicin (the chemical responsible for the 'heat') has 1.6×107 Scoville heat units.[60]

ASTA pungency unit: pepper hotness

ASTA (American Spice Trade Association) pungency unit is based on a scientific method of measuring chili pepper 'heat'. The technique utilizes high performance liquid chromatography to identify and measure the concentrations of the various compounds that produce a heat sensation. Scoville units are roughly 15 times higher than Pungency units while measuring capsaicin, so a rough conversion is to multiply Pungency by 15 to obtain Scoville heat units.[61]

Dol: pain

The dol (from the Latin word for pain, dolor) is a unit of measurement for pain.

James D. Hardy, Herbert G. Wolff, and Helen Goodell of Cornell University proposed the unit based on their studies of pain during the 1940s-1950s. They defined one dol to equal to "just noticeable differences" (jnd's) in pain. The unit never came into widespread use and other methods are now used to assess the level of pain experienced by patients.

Schmidt sting pain index and Starr sting pain index

These are pain scales rating the relative pain caused by different hymenopteran stings. Schmidt has refined his Schmidt Sting Pain Index (scaled from 1 to 4) with extensive anecdotal experience, culminating in a paper published in 1990 which classifies the stings of 78 species and 41 genera of Hymenoptera. The Starr sting pain scale uses the same 1-to-4 scaling. In practice, the Comparative Pain Scale is used by doctors when working with patients.[62]

Erlang: telecommunications traffic volume

The erlang, named after A. K. Erlang, as a dimensionless unit is used in telephony as a statistical measure of the offered intensity of telecommunications traffic on a group of resources. Traffic of one erlang refers to a single resource being in continuous use, or two channels being at fifty percent use, and so on, pro rata. A lot of telecommunications management and forecasting software uses this unit on a day to day basis—but strictly speaking it is a telecom sector specific network stress measurement unit.

Amazon River: large volumes of water flow

The volume of discharge of the Amazon River sometimes used to describe large volumes of water flow such as ocean currents. The unit is equivalent to 216,000 m3/s.[63] See also Sydharb per day.

See also


  1. ^ The firkin is normally a unit of volume equal to nine imperial gallons. The "firkin" of the FFF system is the firkin of water, i.e. the mass of nine imperial gallons of water. The imperial gallon was originally based on the volume of ten pounds of water (under certain thermodynamic conditions). This gives us a water density of ten pounds per imperial gallon. Using this as a basis of our calculation we obtain ninety pounds for the firkin of water.
  2. ^ Furlongs per Fortnight
  3. ^ "c in furlongs per fortnight - Google Search". Retrieved 2006-03-10. 
  4. ^ "FAQ for newsgroup UK.rec.sheds, version 2&3/7th" (TXT). 2000. Retrieved 2006-03-10. 
  5. ^ Attoparsec
  6. ^ The exact length is 29.9792458 cm.
  7. ^ "Rear Admiral Grace Murray Hopper". US Navy. 4 May 2006. Retrieved 2006-12-26. 
  8. ^ NZ fishermen land colossal squid
  9. ^ Nelson has a facelift but loses 16ft
  10. ^ Shores of Lake Agassiz
  11. ^ Computer Recycling and Donating, Electronic Recycling Association Expands its Operations
  12. ^ Enough Burnt Sienna to Circle the Globe
  13. ^ "An Exceptional Nuclear Glossary". 2006-11-25. Retrieved 2011-04-08. 
  14. ^ Russ Rowlett (September 1, 2004). "Units: S". How Many? A Dictionary of Units of Measurement. University of North Carolina at Chapel Hill. Retrieved 2009-12-14. 
  15. ^ Green, Jonathon (December 1987). Dictionary of Jargon. Routledge Kegan & Paul. p. 487. ISBN 0710099193. Retrieved 2009-12-14. 
  16. ^ "The Jargon File - nanoacre". Retrieved 2006-03-10. 
  17. ^ Unit of Measurement
  18. ^ Nigerian crash airline grounded
  19. ^ Grass fire strikes the Malverns
  20. ^ [1]
  21. ^ Expat joins Falklands council
  22. ^ Diary: The Amazon rainforest
  23. ^ "Rhode Island as a Unit of Measure". Retrieved 2006-03-10. 
  24. ^ "The Atlas of Canada". Retrieved 2009-01-22. 
  26. ^ Edwards, Chris (August 2005). "Quizzical: this month, Chris Edwards tackles temperature extremes, the size of Belgium, categorising nations' development status, the hydrogen bombs dropped on Japan and the number of people who speak Scottish Gaelic". Geographical. Retrieved 20 May 2009. 
  27. ^ Husch, Bertram; Thomas W. Beers, John A. Kershaw (2003). Forest Mensuration. John Wiley and Sons. ISBN 0-471-01850-3. 
  28. ^ Wolfram Alpha: Hubble-Barn
  29. ^ Paul Hudson: 3rd anniversary of June 2007 floods, showing a storm water storage tank "half the size of an Olympic swimming pool"
  30. ^ Australian Water Facts - Did You Know?
  31. ^
  32. ^
  33. ^ p "Landfill tax 'costing homes £30'", BBC News website
  34. ^ Atwood, Robert (2006). Bears Can't Run Downhill, and 200 Dubious Pub Facts Explained. Ebury Press. p. 124. ISBN 0091912550. 
  35. ^ "The name "kilogram": a historical quirk". Bureau International des Poids et Mesures. Retrieved 2006-03-10. 
  36. ^
  37. ^ "Frequently Asked Questions, unit weights". Portland Cement Association. 2011. Retrieved 2011-02-15. 
  38. ^ » Giant dinosaur’s fossils found in Spain, largest ever recorded in Europe
  39. ^
  40. ^ "The Pathogenesis and Therapy of Combined Radiation Injury" (PDF). Defense Threat Reduction Agency. Retrieved 2006-11-12. 
  41. ^ Microfortnight
  42. ^ "OpenVMS Frequently Asked Questions (FAQ), Part 3/11". 11 April 2005. EXE$GL_TODR. Retrieved 10 March 2009. 
  43. ^ See, for instance, the current Mean Julian Day, precise to 6 decimal place, from the United States Naval Observatory.
  44. ^ a b Multimillionaire pooch dies at age 12 (84 in dog years). Retrieved 2011-06-12.
  45. ^ "Geologic Time Galactic". "". Retrieved 2006-12-19. 
  46. ^ Furman, Alan T.. "The Cordic Algorithm for Fixed-Point Polar Geometry". FORTH Dimensions (FORTH Interest Group) 4: 14–15. Retrieved 2009-01-16. 
  47. ^ Macleod, William T, ed (1982). Collins Concise Dictionary of the English Language. ISBN 0-00-433091-9. 
  48. ^ The Bible, Old and New Testaments, King James Version - Project Gutenberg
  49. ^ "Terabyte definition". Retrieved 2008-09-03. 
  50. ^ "How the Wayback Machine works". Retrieved 2008-09-03. 
  51. ^ "Data Powers of Ten". 1995. Archived from the original on 2001-01-24. Retrieved 2008-09-03. 
  52. ^ "How much that is that, James S. Huggins' Refrigerator Door". Retrieved 2008-09-03. 
  53. ^ Matt Mahoney (2 November 2010). "Large Text Compression Benchmark". Retrieved 19 November 2010. 
  54. ^
  55. ^ "Big MacCurrencies". The Economist. 1998-04-09. Retrieved 2007-07-24. 
  56. ^ Mars Bar, Nico Colchester Fellowship, (Financial Times website). Article dated 2001-01-26. Retrieved 2007-01-13.
  57. ^ pg 35, Johnson Space Center Oral History Project, interview with Dr. Robert Stevenson
  58. ^ Triumph of the Nerds. PBS.
  59. ^ What Is The Scoville Scale. Retrieved 2008-12-22.
  60. ^ Scoville Scale. Retrieved 2008-12-22.
  61. ^ Tainter, Donna R.; Anthony T. Grenis (2001). Spices and Seasonings. Wiley-IEEE. p. 30. ISBN 0-471-35575-5.  — "Interlab variation [for the original Scoville scale] could be as high as + / - 50%. However, labs that run these procedures could generate reasonably repeatable results."
  62. ^ The Comparative Pain Scale. Retrieved 2010-07-30.
  63. ^ "Amazon River", "Encyclopedia Brittanica", 2010, Retrieved 8 January 2011.

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