Beard-seconds, Chains, Pirate-Ninjas, and other Units of Measure
Most surveyors, engineers and other technical colleagues will have enjoyed at least a semester on dimensional analysis and conversion between units of measure. Laborious although it was, by the end most students were comfortable converting the most arcane combinations of units (so long as you had a wide enough piece of working paper).
With that shared experience in mind, we’ve compiled a collection of units of measure. We have included hectares, for example, which are foundational to our work. However, we’ve also included other UoMs that are historical – or inspired by science fiction, popular culture, technology and beyond.
Let us know about other UoMs you have come across or even used. If possible, include your working!
Unit of Measure |
Description |
Acre |
The (English) acre is a unit of area equal to 43,560 square feet, or 10 square chains, or 160 square poles. It derives from a ploughing area that is 4 poles wide and a furlong (40 poles) long. A square mile is 640 acres. The Scottish acre is 1.27 English acres. The Irish acre is 1.6 English acres. |
Arpent |
Unit of length and area used in France, Louisiana, and Canada. As a unit of length, approximately 191.8 feet (180 old French 'pied', or foot). The (square) arpent is a unit of area, approximately .845 acres, or 36,802 square feet. |
Baker’s dozen |
If you buy a dozen loaves of bread, bakers usually throw one in for free, so baker's dozen means 13. The practice wasn’t consequent of a general air of goodwill toward customers; rather, a 13th century medieval English law made bakers liable for severe punishment should they short-change a customer. Indeed, the law allowed for the amputation of a hand by axe, so it is understandable that English bakers erred on the side of caution by providing 13 baps! |
Barn-megaparsec |
A barn-megaparsec is approximately 2/3 of a teaspoon. The unit is a combination of the unit barn (b), which is a tiny area unit used in nuclear physics, and the megaparsec (Mpc), a very large unit used for measuring distances between galaxies. |
Beard-second |
The beard-second is a unit of length inspired by the light-year, but applicable to extremely short distances such as those in integrated circuits. It is length an average beard grows in one second. Kemp Bennett Kolb defines the distance as exactly 100 angstroms (10 nanometers),[10] as does Nordling and Österman's Physics Handbook. Google Calculator uses 5 nm. |
Big Mac Index (purchase power) |
The Big Mac Index (coined by The Economist) compares the purchasing power parity of countries measured in terms of the cost of a Big Mac hamburger. |
Chain |
Unit of length usually understood to be Gunter’s chain, but possibly variant by locale. See also Rathbone's chain. The name comes from the heavy metal chain of 100 links that was used by surveyors to measure property bounds. |
Colpa |
Old Irish measure of land equal to that which can support a horse or cow for a year. Approximately an Irish acre of good land. |
Compass |
One toise. |
Donkey power |
This facetious engineering unit is defined as 250 watts – about a third of a horsepower. |
Double-decker bus |
In Britain, newspapers and other media will often refer to lengths in comparison to the length (8.4 metres, or 27.6 feet) or height (4.4 metres, or 14.4 feet) of a London double-decker bus. |
Dry sheep equivalent |
The number of not-pregnant sheep a specific land holding can support. |
Engineer's Chain |
A 100 foot chain containing 100 links of one foot apiece. |
Flock |
For all those that thought a flock was any number of birds flying together – no! A flock is specifically 2 score, or 40, birds. |
Furlong |
Unit of length equal to 40 poles (220 yards). Its name derives from "furrow long", the length of a furrow that oxen can plough before they are rested and turned. See Gunter's chain. |
gkB |
A measure of irritation. Swedish in origin, this measured irritation in "gram knäckeBröd", or grams of crispbread crumbs per cm² in a bed where you've just laid down to sleep. |
Ground |
A unit of area equal to 2400 sq. ft., or 220 sq. meters, used in India. |
Gunter's Chain |
Unit of length equal to 66 feet, or 4 poles. Developed by English polymath Edmund Gunter early in the 1600's, the standard measuring chain revolutionized surveying. Gunter's chain was 22 yards long, one tenth of a furlong, a common unit of length in the old days. An area one chain wide by ten chains long was exactly an acre. In 1595 Queen Elizabeth I had the mile redefined from the old Roman value of 5000 feet to 5280 feet in order for it to be an even number of furlongs. A mile is 80 chains. |
Hectare |
Metric unit of area equal to 10,000 square meters, or 2.471 acres, or 107,639 square feet. |
Hide |
A very old English unit of area, a hide was of variable size depending on locale and the quality of the land. It was the amount of land to support a family, and ranged from 60 to 180 acres. After the Norman conquest in 1066 it became standardized at around 120 acres. |
Hundred |
An adminstrative area larger than a village and smaller than a county. In England it was 100 hides in size, and the term was used for early settlements in Virginia, Maryland, and Delaware (USA). |
Jerk |
Based on the jerk many cars have when kicking in a sudden acceleration, auto engineers defined a ‘jerk’ as a UoM for the rate of change of acceleration, with 1 jerk equal to 0.3048 m/sec^{3}. |
Jiffy |
The jiffy comes from the computing field. One jiffy is the duration of one tick of the system timer interrupt. This is usually 0.01 seconds, but in some earlier systems such as the Commodore 8-bit computers the jiffy was defined as 1/60th of a second. |
Labor |
The labor ('labour') is a unit of area used in Mexico and Texas. In Texas it equals 177.14 acres (or 1 million square varas). |
League (legua) |
Unit of area used in the southwest U.S., equal to 25 labors, or 4428 acres (Texas), or 4439 acres (California). Also, a unit of length-- approximately three miles. |
Link |
Unit of length equal to 1/100 chain (7.92 inches). |
MegaFonzie |
A MegaFonzie is a fictional unit of measurement of an object's coolness invented by Professor Farnsworth in the Futurama episode, "Bender Should Not Be Allowed on TV." A 'Fonzie' is about the amount of coolness inherent in the Happy Days character Fonzie. |
Megalithic yard |
After analysing survey data from over 250 stone circles in England and Scotland, Scottish professor of engineering Alexander Thom came to the conclusion that there must have been a common unit of measure which he called a megalithic yard (which was the equivalent of 0.9074 yards, or 0.8297 metres). |
Mickey (as in, Mouse) |
One mickey (named after Mickey Mouse) is the length of the smallest detectable movement of a computer mouse. This is about 0.1 mm, but its exact size depends on the equipment used. |
Moment |
If you ask someone to wait a moment, you are asking them to wait for a very short period of time. How short? Turns out a moment is a medieval unit of time equals to 1/40th of an hour or 1.5 minutes. |
Moot |
One smoot is defined to be equal to five feet and seven inches (1.70 m), the height of Oliver R. Smoot. He was an MIT student whose fraternity pledge in 1958 was to be used to measure the length of the Harvard Bridge. The bridge’s length was measured to be 364.4 smoots plus or minus one ear. Perhaps it was fate that Oliver Smoot later became Chairman of the American National Standards Institute (ANSI) and President of the International Organization for Standardization (ISO). |
Morgen |
Unit of area equal to about .6309 acres. It was used in Germany, Holland and South Africa, and was derived from the German word Morgen ("morning"). It represented the amount of land that could be ploughed in a morning. |
Nibble |
As a quantity of data, a nibble is equal to 4 bits, half an 8-bit byte. It’s a convenient unit since it fits exactly one hexadecimal digit. |
Out |
An 'out' was ten chains. When counting out long lines, the chain carriers would put a stake at the end of a chain, move the chain and put a stake at the end, and so on until they ran "out" of ten stakes. |
Perch |
See pole. |
Pirate-Ninja |
A pirate-ninja is defined as one kilowatt-hour (3.6 MJ) per Martian day, or sol. It is equivalent to approximately 40.55 watts. Andy Weir, author of The Martian, revealed in a 2015 interview with Adam Savage that the Curiosity rover team at the Jet Propulsion Laboratory references milli-pirate-ninjas in their meetings |
Point |
A point of the compass. There are four cardinal points (North, South, East, West), and 28 others yielding 32 points of 11.25 degrees each. A survey line's direction could be described as a compass point, as in "NNE" (north northeast). To improve precision, the points would be further subdivided into halves or quarters as necessary, for example, "NE by North, one quarter point North". In some areas, "and by" meant one half point, as in "NE and by North". |
Pole |
Unit of length and area. Also known as a perch or rod. As a unit of length, equal to 16.5 feet. A mile is 320 poles. As a unit of area, equal to a square with sides one pole long. An acre is 160 square poles. It was common to see an area referred to as "87 acres, 112 poles", meaning 87 and 112/160 acres. |
Pueblo |
A Spanish grant of less than 1000 acres. |
Rancho |
A Spanish grant of more than 1000 acres. |
Rathbone's Chain |
A measuring chain two poles, or 33 feet, in length. |
Rod |
See pole. |
Rood |
Unit of area usually equal to 1/4 acre. |
Shake (as in, two shakes of a lamb’s tail) |
In nuclear physics, a shake is 10 nanoseconds, the approximate time for a generation within a nuclear chain reaction. The term comes from the expression ‘two shakes of a lamb's tail’, meaning quickly. |
Sheppy |
A sheppey is defined as the closest distance at which sheep remain picturesque, which is about 7/8 of a mile. The unit is the creation of Douglas Adams and John Lloyd, included in The Meaning of Liff, their dictionary of objects for which no name exists. |
Slug |
The slug is an English unit of mass – it is better considered in Imperial measurement, as it’s an old English mass UoM. A slug is defined as the mass that accelerates by 1 ft/s² when a force of one pound-force (lbf) is exerted on it (14.6 kg). |
Toise |
Traditional French unit of length equal to 6 old French 'pieds' or feet, or 6.4 English feet. |
Vara |
Unit of length (the "Spanish yard") used in the U.S. southwest. The vara is used throughout the Spanish speaking world and has values around 33 inches, depending on locale. The legal value in Texas was set to 33 1/3 inches early in the 1900's. |
Virgate |
An old English unit of area, equal to one quarter of a hide. The amount of land needed to support a person. |
Warhol (unit of fame-time) |
Derived from Andy Warhol’s statement that ‘everyone will be world-famous for fifteen minutes’, a Warhol represents fifteen minutes of fame. It can be used in multiples:
§ 1 kilowarhol — famous for 15,000 minutes, or 10.42 days. § 1 megawarhol — famous for 15 million minutes, or 28.5 years. |
Wiffle |
A Wiffle, also referred to as a WAM for Wiffle (ball) Assisted Measurement, is equal to a sphere 89 millimeters (3.5 inches) in diameter – the size of a Wiffle ball, a perforated, light-weight plastic ball frequently used by marine biologists as a size reference in photos to measure corals and other objects. The spherical shape makes it omnidirectional and perfect for taking a speedy measurement, and the open design also allows it to avoid being crushed by water pressure. Wiffle balls are a much cheaper alternative to using two reference lasers, which often pass straight through gaps in thin corals. |