Bohr radius
The Bohr radius (a0) is a physical constant, approximately equal to the most probable distance between the nucleus and the electron in a hydrogen atom in its ground state. It is named after Niels Bohr
Horse length
A horse length, or simply length, is a unit of measurement for the length of a horse from nose to tail, approximately 8 feet (2.4 m).
Optical unit
Optical units are dimensionless units of length used in optical microscopy. They are used to express distances in terms of the numerical aperture of the system and the wavelength of the light used for
Wa (unit)
Wa (Thai: วา [wāː], also waa or wah, abbreviated ว.) is a unit of length, equal to two metres (2 m) or four sok (ศอก.) Wa as a verb means to outstretch (one's) arms to both sides, which relates to the
Stadion (unit)
The stadion (plural stadia, Greek: στάδιον; latinized as stadium), also anglicized as stade, was an ancient Greek unit of length, consisting of 600 Ancient Greek feet (podes).
ISO 2848
ISO 2848 (Building construction – Modular coordination – Principles and rules) is an international standard for the construction industry that describes the aims of modular coordination and gives the
Toise
A toise (French pronunciation: [twaz]; symbol: T) is a unit of measure for length, area and volume originating in pre-revolutionary France. In North America, it was used in colonial French establishm
Ald (unit)
Ald is an obsolete Mongolian measure equal to the length between a man's outstretched arms. An ald is therefore approximately equal to 160–180 cm (63–71 in)
Earth's circumference
Earth's circumference is the distance around Earth. Measured around the Equator, it is 40,075.017 km (24,901.461 mi). Measured around the poles, the circumference is 40,007.863 km (24,859.734 mi). Mea
Ken (unit)
The ken (間) is a traditional Japanese unit of length, equal to six Japanese feet (shaku). The exact value has varied over time and location but has generally been a little shorter than 2 meters (6 ft
Li (unit)
Li (Chinese: 里, lǐ, or 市里, shìlǐ), also known as the Chinese mile, is a traditional Chinese unit of distance. The li has varied considerably over time but was usually about one third of an English mil
Fistmele
Fistmele, also known as the "brace height", is an older term used in archery to describe the correct distance (about seven inches, for a Northern European or English longbow) between a bow and its str
Kadem
Kadem (also ayak آیاق) is a defunct measurement unit used in the Ottoman Empire. Kadem means "foot" and during the last years of the Ottoman Empire 1 kadem was set to be 30.48 cm (1.000 ft) in accorda
Stick (unit)
The stick may refer to several separate units, depending on the item being measured.
Cicero (typography)
A cicero /ˈsɪsəroʊ/ is a unit of measure used in typography in Italy, France and other continental European countries, first used by Pannartz and Sweynheim in 1468 for the edition of Cicero's Epistula
Hand (unit)
The hand is a non-SI unit of measurement of length standardized to 4 in (101.6 mm). It is used to measure the height of horses in many English-speaking countries, including Australia, Canada, the Repu
Chi (unit)
The chi (Tongyong Pinyin chih) is a traditional Chinese unit of length. Although it is often translated as the "Chinese foot", its length was originally derived from the distance measured by a human h
Em (typography)
An em (from English em quadrat) is a unit in the field of typography, equal to the currently specified point size. For example, one em in a 16-point typeface is 16 points. Therefore, this unit is the
Point (typography)
In typography, the point is the smallest unit of measure. It is used for measuring font size, leading, and other items on a printed page. The size of the point has varied throughout printing's history
Himetric
Himetric is a resolution-independent unit of length. Its role is similar to the twip, but it is one hundredth of a millimetre. It is mainly used in Object Linking and Embedding and derived technologie
Nalva
Nalva (from Sanskrit नल्व nalva) is a measure of distance equal to 400 Hastas (Cubits). That is equal to 9600 Aṅgula, which is believed to be equal to approximately 180 metres. Used in Mahābhārata.
Typographic unit
Typographic units are the units of measurement used in typography or typesetting. Traditional typometry units are different from familiar metric units because they were established in the early days o
Schoenus
Schoenus (Latin: schœnus; Greek: σχοίνος, schoinos, lit. "rush rope"; Ancient Egyptian: i͗trw, lit. "river-measure") was an ancient Egyptian, Greek and Roman unit of length and based on the knotted co
Astronomical unit
The astronomical unit (symbol: au, or AU or AU) is a unit of length, roughly the distance from Earth to the Sun and approximately equal to 150 million kilometres (93 million miles) or 8.3 light-minute
Cun (unit)
A cun (Chinese: 寸), often glossed as the Chinese inch, is a traditional Chinese unit of length. Its traditional measure is the width of a person's thumb at the knuckle, whereas the width of the two fo
Gauge (firearms)
The gauge (or commonly bore in British English) of a firearm is a unit of measurement used to express the inner diameter (bore diameter) of the barrel. Gauge is determined from the weight of a solid s
Twip
A twip (abbreviating "twentieth of a point", "twentieth of an inch point", or "twentieth of an Imperial point") is a typographical measurement, defined as 1⁄20 of a typographical point. One twip is 1⁄
Barleycorn (unit)
The barleycorn is an English unit of length equal to 1⁄3 of an inch (i.e. about 8.47 mm). It is still used as the basis of shoe sizes in English-speaking countries.
Bolt (cloth)
A bolt is a piece of cloth woven on a loom or created by a knitting machine, as it is processed, stored and/or marketed. Consequently, its dimensions are highly variable – flexible and dependent upon
Skein (unit)
A skein is a unit of length which has been used in the UK.As a measuring unit of cotton yarn or of silk, a skein equates to a "rap" or a "lea". One skein is equivalent to 360 feet (109.73 m).
Mile
The mile, sometimes the international mile or statute mile to distinguish it from other miles, is a British imperial unit and United States customary unit of distance; both are based on the older Engl
Arşın
An arşın (Ottoman Turkish: آرشين or آرشون) is an old Turkish unit of length, about 27 inches (690 mm) long. The word means 'arm' and thus the measure corresponds to a yard.
Rope (unit)
A rope may refer to any of several units of measurement initially determined or formed by ropes or knotted cords.
Metric mile
A metric mile is a colloquial term used in some countries for the 1500 meters, the premier middle distance running event in international track and field. The term 'metric mile' (0.93 statute miles) w
Pica (typography)
The pica is a typographic unit of measure corresponding to approximately 1⁄6 of an inch, or from 1⁄68 to 1⁄73 of a foot. One pica is further divided into 12 points. In printing, three pica measures ar
Alen (unit of length)
Alen or aln is a traditional Scandinavian unit of distance similar to the north German elle: roughly 60 centimeters. The Danish alen, also used in Norway, was equal to 62.77 centimeters (2 Danish fod)
Zhàng
The zhang (Chinese: 丈) is a customary Chinese unit of length equal to 10 chi (Chinese feet). Its value varied over time and place with different values of the chi, although it was occasionally standar
Hvat
Hvat (Serbian: Хват) is a historical unit of length that was common in Croatia and Serbia analogous to fathom. The measurement system based on the hvat is called hvatski sistem (literally "hvat system
Nautical mile
A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. Historically, it was defined as the meridian arc length corresponding to on
Spat (distance unit)
The spat (symbol S) is an obsolete unit of distance used in astronomy. It is equal to 1,000,000,000 kilometres (620,000,000 mi; 6.7 au).
Scantling
Scantling is a measurement of prescribed size, dimensions, or cross sectional areas.
Sahasra
A Sahasra (Sanskrit: सहस्र) is a Vedic measure of Count data, which was chiefly used in ancient as well as medieval India. A Sahasra means 1k, i.e. 1000 Count data
Walking distance measure
The walking distance measure denotes the distance that can be travelled by walking in a fixed amount of time. In Japan, the standard measure for walking distance is 80 meters for 1 minute of walking t
Megalithic yard
The megalithic yard is a hypothetical ancient unit of length equal to about 2.72 feet (0.83 m). Some researchers believe it was used in the construction of megalithic structures. The proposal was made
Gunter's chain
Gunter's chain (also known as Gunter’s measurement) is a distance measuring device used for surveying. It was designed and introduced in 1620 by English clergyman and mathematician Edmund Gunter (1581
Solar radius
Solar radius is a unit of distance used to express the size of stars in astronomy relative to the Sun. The solar radius is usually defined as the radius to the layer in the Sun's photosphere where the
League (unit)
A league is a unit of length. It was common in Europe and Latin America, but is no longer an official unit in any nation. Derived from an ancient Celtic unit and adopted by the Romans as the leuga, th
Girah
A girah (also geerah) was a unit of length in India and Pakistan approximately equal to 2.25 inches (5.715 cm). After metrication by both countries in the mid-20th century, the unit became obsolete.
Lachter
The lachter (also Berglachter) was a common unit of length used in the mining industry in Europe, usually to measure depth, tunnel driving and the size of mining fields; it was also used for contract
Light-second
The light-second is a unit of length useful in astronomy, telecommunications and relativistic physics. It is defined as the distance that light travels in free space in one second, and is equal to exa
Guz
A guz or the Mughal yard is a unit of length used in parts of Asia. Historically, it was a regionally variable measurement similar to the English yard both in size and in that it was often used for me
Lea (unit)
The lea or lay was a British unit of length. The Oxford English Dictionary describes it as a measure "of varying quantity". It cites quotations from within various areas of the textile industry, which
Hat'h
A hat'h (hath, hand, cubit, moolum or mulam) is an obsolete unit of length in India equal to 24 (approximately 18 inches) or 2 hat'h to a gaz (approximately 1 yard). The unit was used in Mumbai (forme
Thousandth of an inch
A thousandth of an inch is a derived unit of length in a system of units using inches. Equal to 1⁄1000 of an inch, a thousandth is commonly called a thou /ˈθaʊ/ (used for both singular and plural) or
Bamboo (unit)
A bamboo is an obsolete unit of length in India and Myanmar.
Pace (unit)
A pace is a unit of length consisting either of one normal walking step (approximately 0.75 metres or 30 inches), or of a double step, returning to the same foot (approximately 1.5 metres or 60 inches
Device-independent pixel
A device-independent pixel (also: density-independent pixel, dip, dp) is a unit of length. A typical use is to allow mobile device software to scale the display of information and user interaction to
Palm (unit)
The palm is an obsolete anthropic unit of length, originally based on the width of the human palm and then variously standardized. The same name is also used for a second, rather larger unit based on
Span (unit)
A span is the distance measured by a human hand, from the tip of the thumb to the tip of the little finger. In ancient times, a span was considered to be half a cubit. Sometimes the distinction is mad
Paris inch
The Paris inch or pouce is an archaic unit of length that, among other uses, was common for giving the measurement of lenses. The Paris inch could be subdivided into 12 Paris lines (ligne), and 12 Par
Penny (unit)
In the United States, the length of a nail is designated by its penny size, written with a number and the abbreviation d for penny; for example, 10d for a ten-penny nail. A larger number indicates a l
Geographical mile
The geographical mile is a unit of length determined by 1 minute of arc along the Earth's equator. For the international ellipsoid 1924 this equalled 1855.4 metres. The American Practical Navigator 20
Horizontal pitch
Horizontal pitch (HP) is a unit of length defined by the Eurocard printed circuit board standard used to measure the horizontal width of rack mounted electronic equipment, similar to the rack unit (U)
Parasang
The parasang is a historical Iranian unit of walking distance, the length of which varied according to terrain and speed of travel. The European equivalent is the league. In modern terms the distance
Muggeseggele
A Muggeseggele or Muckenseckel is a humorous Alemannic German idiom used in Swabia to designate a nonspecific very small length or amount of something; it refers to a housefly's scrotum. It has been c
Sana lamjel
Sana lamjel was a customary unit of length used in the erstwhile kingdom of Manipur, now a state of India. The unit of length, defined by the ruler of the kingdom, in 33 CE, being equal to the distanc
Endaze
Endaze is a defunct measurement unit of length used in the Ottoman Empire. Endaze means pace. But it is shorter than the pace. It was equal to 65.25 cm. It was usually used in the silk trade. Its sub
Unit of length
A unit of length refers to any arbitrarily chosen and accepted reference standard for measurement of length. The most common units in modern use are the metric units, used in every country globally. I
Digit (unit)
The digit or finger is an ancient and obsolete non-SI unit of measurement of length. It was originally based on the breadth of a human finger. It was a fundamental unit of length in the Ancient Egypti
Finger (unit)
A finger (sometimes fingerbreadth or finger's breadth) is any of several units of measurement that are approximately the width of an adult human finger, including: The digit, also known as digitus or
Bahar (unit)
Bahar (Arabic: بـهـﺭ) is an obsolete unit of measurement.
* In Iran it was a unit of length approximately equal to 3.25 cm (1.28 in)
* In Oman, it was a unit of mass equal to approximately 808 g (1.
Tlalcuahuitl
Tlalcuahuitl [t͡ɬaɬˈkʷawit͡ɬ] or land rod also known as a cuahuitl [ˈkʷawit͡ɬ] was an Aztec unit of measuring distance that was approximately 2.5 m (8.2 ft), 6 ft (1.8 m) to 8 ft (2.4 m) or 7.5 ft (2.
Klafter
The klafter is an historical unit of length, volume and area that was used in Central Europe.
Biblical mile
Biblical mile (Hebrew: מיל, romanized: mīl) is a unit of distance on land, or linear measure, principally used by Jews during the Herodian dynasty to ascertain distances between cities and to mark the
Lunar distance (astronomy)
The instantaneous Earth–Moon distance, or distance to the Moon, is the distance from the center of Earth to the center of the Moon. Lunar distance (LD or ), or Earth–Moon characteristic distance, is a
Arabic mile
The Arab, Arabic, or Arabian mile (Arabic: الميل, al-mīl) was a historical Arabic unit of length. Its precise length is disputed, lying between 1.8 and 2.0 km. It was used by medieval Arab geographers
Step (unit)
A step (Latin: gradus, pl. gradūs) was a Roman unit of length equal to 2½ Roman feet (pedes) or ½ Roman pace (passus). Following its standardization under Agrippa, one step was roughly equivalent to 0
Light-year
A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (9.46×1012 km), or 5.88 trillion mi
Aṅgula
Aṅgula (from Sanskrit: अङ्गुल aṅgula - 'a finger; the thumb; a finger's breadth') is a measure of length. Twelve aṅgulas make a Vitasti or span, and twenty-four a Hasta or Cubit. 108 Angulam make a 'D
Yard
The yard (symbol: yd) is an English unit of length in both the British imperial and US customary systems of measurement equalling 3 feet or 36 inches. Since 1959 it has been by international agreement
Scandinavian mile
A Scandinavian mile (Norwegian and Swedish: mil, [miːl], like "meal") is a unit of length common in Norway and Sweden, but not Denmark. Today, it is standardised as 1 mil being 10 kilometres (6.2 mile
Day's journey
A day's journey in pre-modern literature, including the Bible, ancient geographers and ethnographers such as Herodotus, is a measurement of distance. In the Bible, it is not as precisely defined as ot
Traditional point-size names
Fonts originally consisted of a set of moveable type letterpunches purchased from a type foundry. As early as 1600, the sizes of these types—their "bodies"—acquired traditional names in English, Frenc
Agate (typography)
An agate (US) or ruby (UK) is a unit of typographical measure. It is 5.5 typographical points, or about 1⁄13 inch (1.94 mm). It can refer either to the height of a line of type or to a font that is 5.
Line (unit)
The line (abbreviated L or l or ‴ or lin.) was a small English unit of length, variously reckoned as 1⁄10, 1⁄12, 1⁄16, or 1⁄40 of an inch. It was not included among the units authorized as the British
Unglie
A unglie ("finger") is an obsolete unit of length equal to three-fourths of an inch (1.905 cm) that was used in India and Pakistan. After metrification in both countries, the unit became obsolete.
Rack unit
A rack unit (abbreviated U or RU) is a unit of measure defined as 1+3⁄4 inches (44.45 mm). It is most frequently used as a measurement of the overall height of 19-inch and 23-inch rack frames, as well
Uncia (unit)
The uncia (plural: unciae) was a Roman unit of length, weight, and volume. It survived as the Byzantine liquid ounce (Greek: οὐγγία, oungía) and the origin of the English inch, ounce, and fluid ounce.
Centisome
A centisome is a unit of length defined as one percent of the length of a particular chromosome. This course unit of physical DNA length began to be used in the early exploration of genomes through mo
Jow (unit)
A jow (also called a jacob) is an obsolete unit of length in India approximately equal 0.25 inch (about 0.63 cm). After metrication in India in the mid-20th century, the unit became obsolete.
Rod (unit)
The rod, perch, or pole (sometimes also lug) is a surveyor's tool and unit of length of various historical definitions, often between approximately 3 and 8 meters (9 ft 10 in and 26 ft 2 in). In moder
Shaku (unit)
Shaku (Japanese: 尺) or Japanese foot is a Japanese unit of length derived (but varying) from the Chinese chi, originally based upon the distance measured by a human hand from the tip of the thumb to t
Inch
The inch (symbol: in or ″) is a unit of length in the British imperial and the United States customary systems of measurement. It is equal to 1/36 yard or 1/12 of a foot. Derived from the Roman uncia
Kos (unit)
The kos (Hindi: कोस), also spelled coss, koss, kosh, krosh, and krosha, is a unit of measurement which is derived from a Sanskrit term, क्रोश krośa, which means to "call", as the unit was supposed to
X unit
The x unit (symbol xu) is a unit of length approximately equal to 0.1 pm (10−13 m). It is used to quote the wavelength of X-rays and gamma rays. Originally defined by the Swedish physicist Manne Siegb
Shaftment
The shaftment is an obsolete unit of length defined since the 12th century as 6 inches, which nowadays is exactly 152.4 mm. A shaftment was traditionally the width of the fist and outstretched thumb.
Rood (unit)
A rood (/ˈruːd/; abbreviation: ro) is a historic English and international inch-pound measure of area, as well as an archaic English measure of length.
Nail (unit)
A nail, as a unit of cloth measurement, is generally a sixteenth of a yard or 21⁄4 inches (5.715 cm). The nail was apparently named after the practice of hammering brass nails into the counter at shop
Canna (unit)
Canna (pl. canne; proper meaning in Italian: Cane) was an ancient Italian unit of length, which differed from place to place.
* Capua: 2.1768707 m (9th – 15th centuries)
* Republic of Genoa: 2.49095
Siriometer
The siriometer is an obsolete astronomical unit of length, defined to be equal to one million astronomical units (au). One siriometer is approximately 149.6 petametres; 4.848 parsecs; 15.81 light-year
Fall (unit)
A fall or fa’ is a Scottish measurement of length. Other variants of the name include "faw", "faa" and "fa"; the spelling with an apologetic apostrophe is not favoured now. The measurement was mostly
Hair's breadth
A hair's breadth, or the width of human hair, is used as an informal unit of a very short length. It connotes "a very small margin" or the narrowest degree in many contexts.
Cable length
A cable length or length of cable is a nautical unit of measure equal to one tenth of a nautical mile or approximately 100 fathoms. Owing to anachronisms and varying techniques of measurement, a cable
Fathom
A fathom is a unit of length in the imperial and the U.S. customary systems equal to 6 feet (1.8288 m), used especially for measuring the depth of water. The fathom is neither an International Standar
Pous
The pous (pl. podes; Greek: ποῦς, poûs) or Greek foot (pl. feet) was a Greek unit of length. It had various subdivisions whose lengths varied by place and over time. 100 podes made up one plethron, 60
Cana (unit)
A cana was a unit of length used in the former Crown of Aragon. The exact meaning was not consistent, but the use in Barcelona was a distance of 1.57 metres (5 ft 2 in). It is around the same value as
Link (unit)
The link (usually abbreviated as "l.", "li." or "lnk."), sometimes called a Gunter’s link, is a unit of length formerly used in many English-speaking countries. In US customary units modern definition
Furlong
A furlong is a measure of distance in imperial units and United States customary units equal to one eighth of a mile, equivalent to 660 feet, 220 yards, 40 rods, 10 chains or approximately 201 metres.
Foot (unit)
The foot (pl. feet), standard symbol: ft, is a unit of length in the British imperial and United States customary systems of measurement. The prime symbol, ′, is a customarily used alternative symbol.
Verst
A verst (Russian: верста, versta) is an obsolete Russian unit of length defined as 500 sazhen. This makes a verst equal to 1.0668 kilometres (3,500 feet).
Chain (unit)
The chain is a unit of length equal to 66 feet (22 yards). It is subdivided into 100 links or 4 rods. There are 10 chains in a furlong, and 80 chains in one statute mile. In metric terms, it is 20.116
Kan (unit)
The kan (Korean: 간; Hanja: 間) is a traditional unit of measurement used in Korean architecture still found in use today primarily to describe palaces, Buddhist temples and shrines, and Confucian schoo
Arpent
An arpent (French pronunciation: [aʁpɑ̃], sometimes called arpen) is a unit of length and a unit of area. It is a pre-metric French unit based on the Roman actus. It is used in Quebec, some areas of
Angstrom
The angstrom (/ˈæŋstrəm/, /ˈæŋstrʌm/; ANG-strəm, ANG-strum) or ångström is a metric unit of length equal to 10−10 m; that is, one ten-billionth (US) of a metre, a hundred-millionth of a centimetre, 0.
Parsec
The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to 3.26 light-years or 206,000 astronomical units
Fersah
Fersah was an Ottoman unit of distance. It was based on the distance covered by a horse in normal gait per hour. Its modern definition (parasang) is 5.685 km (3.532 mi). There were other definitions.
Romanian units of measurement
The measures of the old Romanian system varied greatly not only between the three Romanian states (Wallachia, Moldavia, Transylvania), but sometimes also inside the same country. The origin of some of
Paris point
The Paris point is a unit of length defined as 2⁄3 centimetre (6.67 mm; 0.262 in). It is commonly used for shoe sizes in Continental Europe. The unit was invented by French shoemakers in the early 180
Modulor
The Modulor is an anthropometric scale of proportions devised by the Swiss-born French architect Le Corbusier (1887–1965). It was developed as a visual bridge between two incompatible scales, the Impe
Yojana
A yojana (Sanskrit: योजन; Thai: โยชน์; Burmese: ယူဇနာ) is a measure of distance that was used in ancient India, Thailand and Myanmar. A yojana is about 12–15 km.
Cubit
The cubit is an ancient unit of length based on the distance from the elbow to the tip of the middle finger. It was primarily associated with the Sumerians, Egyptians, and Israelites. The term cubit i
Seconds pendulum
A seconds pendulum is a pendulum whose period is precisely two seconds; one second for a swing in one direction and one second for the return swing, a frequency of 0.5 Hz.
Arş
An arş (Ottoman Turkish آرش) is an old Turkish unit of length. The word means 'forearm' and thus the measure corresponds to a cubit.
Ell
An ell (from Proto-Germanic *alinō, cognate with Latin ulna) is a northwestern European unit of measurement, originally understood as a cubit (the combined length of the forearm and extended hand). Th
Thneap
No description available.
Ligne
The ligne (pronounced [liɲ] ), or line or Paris line, is a historic unit of length used in France and elsewhere prior to the adoption of the metric system in the late 18th century, and used in various
Hasta (unit)
The hasta (Sanskrit: हस्त (hásta); Chinese: 肘 (pinyin: zhǒu)) is a traditional Indian unit of length, measured from the elbow to the tip of the middle finger. It equals 24 aṅgulas orﾠ about 18 inches,
Smoot
The smoot /ˈsmuːt/ is a nonstandard, humorous unit of length created as part of an MIT fraternity prank. It is named after Oliver R. Smoot, a fraternity pledge to Lambda Chi Alpha, who in October 1958