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 not exact since it includes units such as the week or the light-year are quite "usual" in the sense that they are often used but which can be "unusual" if taken out of their common context, as demonstrated by the Furlong/Firkin/Fortnight (FFF) system of units.
Many of the unusual units of measurements listed here are colloquial measurements, units devised to compare a measurement to common and familiar objects.
Length
Rack unit
One rack 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 4U server enclosure (case) is seven inches (177.8 mm) high.Hand
The hand 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, Canada, the United Kingdom, Ireland and the United States.Light-nanosecond
The light-nanosecond is defined as exactly 29.9792458 cm. It 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." 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 found many uses 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.Metric foot
A metric foot (defined as 300 mm, or about 11.8 inches) has been used occasionally in the UK but has never been an official unit.Horse
Horses are used to measure distances in horse racing – a horse length (shortened to merely a length when the context makes it obvious) equals roughly 8 feet or 2.4 metres. Shorter distances are measured in fractions of a horse length; also common are measurements of a full or fraction of a head, a neck, or a nose.Boat length
In rowing races such as the Oxford and Cambridge Boat Race, the margin of victory and of defeat is expressed in fractions and multiples of lengths. The length of a rowing eight is about 62 feet (19 m). A shorter distance is the canvas, which is the length of the covered part of the boat between the bow and the bow oarsman. The Racing Rules of Sailing also makes heavy use of boat lengths.Football field (length)
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.An American 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.
A Canadian football field is 65 yd (59 m) wide and 150 yd (140 m) long, including two 20 yd (18 m) long end zones.
Media in the UK also use the football pitch as a unit of length, although the area of the association football pitch is not fixed, but may vary within limits of 90–120 m (98–131 yd) in length and 45–90 m (49–98 yd) in width. The usual size of a football pitch is 105 m × 68 m (115 yd × 74 yd), the dimensions used for matches in the UEFA Champions League.
Block
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). Sometimes people living in cities with a regularly spaced street grid will speak of long blocks and short 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 the Manhattan Metric).
The Earth's circumference
The circumference of a great circle of the Earth (about 40,000 km or 25,000 mi or 22,000 nmi) 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". According to WGS-84, the circumference of a circle through the poles (twice the length of a meridian) is 40,007,862.917 metres (43,753,130.924 yd) and the length of the equator is 40,075,016.686 metres (43,826,571.179 yd). 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.
The definitions of both the nautical mile and the kilometre were originally derived from the Earth's circumference as measured through the poles. The nautical mile was defined as a minute of arc of latitude measured along any meridian. A circle has 360 degrees, and each degree is 60 minutes, so the nautical mile was defined as 1⁄21,600 of the Earth's circumference, or about 1,852.22 metres. However, by international agreement, it is now defined to be exactly 1,852 metres (6,076 ft).
The metre was originally defined as 1⁄10,000,000 of the distance from a pole to the equator, or as 1⁄40,000,000 of the Earth's circumference as measured through the poles. This standard made the historical metre 0.0197% longer than the modern standard metre, which is calculated based on the distance covered by light in a vacuum in a set amount of time.
Earth-to-Moon distance
The distance between the Earth's and the Moon's surfaces is, on average, approximately 380,000 km or 240,000 miles. This distance is sometimes used in the same manner as the circumference of the Earth; that is, 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 abbreviation for the Earth-to-Moon distance is "LD" which stands for "Lunar Distance", used in astronomy to express close approaches of Earth by minor planets.
Siriometer
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.
Area
Barn
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 for cross sections in nuclear and particle physics. Additional units include the microbarn (or "outhouse") and the yoctobarn (or "shed").
Brass
One brass is 100 square feet (9.29 m2) area (used in measurement of work done or to be done, such as plastering, painting, etc.). It is also equal, however, to 100 cubic feet (2.83 m3) of estimated or supplied loose material, such as sand, gravel, rubble, etc. This unit is prevalent in construction industry in India.
Square
The square is an Imperial unit of area that is used in the construction industry in North America,[13] and was historically used in Australia by real estate agents. One square is equal to 100 square feet (9.29 m2). A roof's area may be calculated in square feet, then converted to squares.
Cow's grass
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.
Football field (area)
On this schema, an association football field is used to help to conceptualize the size of a polo field.
A football pitch, or field, can be used as a man-in-the-street unit of area. The standard FIFA football pitch 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 ft) in length and 4 m (13 ft) in width in either direction (and even larger discretions if the pitch is not used for international competition), which generally results in the association football pitch generally only being used for order of magnitude comparisons.
An American 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). A Canadian 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).
An Australian 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.
Morgen
A morgen ("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. This unit of measure was also used in the Dutch colonial province of New Netherland (later New York and parts of New England).
Countries, regions, and cities
The area of a familiar country, state or city is often used as a unit of measure, especially in journalism.
Wales
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". 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.
In older British and Commonwealth atlases, it was common to show a known area at the same scale, and the usual area to show was either Wales for smaller scales, or Great Britain for larger areas.
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 programme More or Less introduced the idea of "kilowales" – an area 1,000 times the size of Wales. The Register introduced the nanowales (20.78 m2).
The measurement has been adopted by rainforest conservation charity Size of Wales, aiming to conserve an area of rainforest equating to the area of Wales. On 1 March 2013, the charity announced that they had succeeded in conserving an area of rainforest the size of Wales and will continue to operate to sustain and increase the protected area.
The United States
In the United States the area of the smallest state, Rhode Island (1,545 sq mi or 4,000 km2), the largest of the contiguous 48 states, Texas (268,601 sq mi or 695,670 km2), and, less commonly, Alaska (656,425 sq mi or 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. In the 1979 movie The China Syndrome, radiation is expected to contaminate "an area the size of Pennsylvania". Any state may be used in this fashion to describe the area of another country.
The US Central Intelligence Agency uses Washington, D.C. (61.4 sq mi or 159 km2) as a comparison for city-sized objects.[citation needed]
Other countries
In the Netherlands, its smallest province, Utrecht (1,386 km2 or 535 sq mi), is often used as a comparison for regions in general.
The country of Belgium (30,528 km2 or 11,787 sq mi) has also often been used when comparing areas, to the point where it has been regarded as a meme 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. It has sometimes been used in attempts to examine whether a certain amount of a given object or group would fit in a space its size; in 2018, it was estimated that approximately 2.6 billion people could fit on the Isle of Wight, at a population density of six people per square metre.
In Denmark, the island of Bornholm (588 square kilometers) is often used to describe the size of an area.
In Germany, the Saarland (2,569.69 km2 or 992.16 sq mi) is often used to define areas.
In Brazil, it is common to compare relatively small areas to the state of Sergipe (21,910.4 km2 or 8,459.7 sq mi), the smallest in the country. Smaller areas are sometimes compared to the cities of São Paulo (1,521.11 km2 or 587.30 sq mi) or Rio de Janeiro (1,221 km2 or 471 sq mi).
