| Square hands (sq hh) | Square miles (sq mi) |
|---|---|
| 1 Square hand | 0.00000000398556269768 sq mi |
| 2 Square hands | 0.00000000797112539537 sq mi |
| 3 Square hands | 0.0000000119566880931 sq mi |
| 4 Square hands | 0.0000000159422507907 sq mi |
| 5 Square hands | 0.0000000199278134884 sq mi |
| 10 Square hands | 0.0000000398556269768 sq mi |
| 20 Square hands | 0.0000000797112539537 sq mi |
| 25 Square hands | 0.0000000996390674421 sq mi |
| 50 Square hands | 0.000000199278134884 sq mi |
| 100 Square hands | 0.000000398556269768 sq mi |
| Reference | Square hands (sq hh) | Square miles (sq mi) |
|---|---|---|
| A sheet of A4 paper | 6.04211 sq hh | 0.0000000240812 sq mi |
| A tennis court | 25265.1 sq hh | 0.000100695 sq mi |
| A football pitch | 691689 sq hh | 0.00275677 sq mi |
| One hectare | 968752 sq hh | 0.00386102 sq mi |
| Central Park, New York | 330344411 sq hh | 1.31661 sq mi |
The square hand is a unit of area equal to sixteen square inches, or 103.2256 square centimetres. Its symbol is sq hh. A hand is four inches, so a square hand is a square four inches on a side, roughly the area of an adult palm. It is a complete and consistent unit that almost nobody has ever needed, because the hand it derives from measures one thing only.
That one thing is horses. The height of a horse or pony is measured at the withers, the ridge between the shoulder blades, and it is given in hands almost everywhere in the world, including in countries that are otherwise entirely metric. A hand was fixed at four inches by an English statute of 1541 under Henry VIII, and the equestrian world has held to that figure ever since.
The notation contains a trap worth knowing. A horse described as 15.2 hands is not fifteen and two tenths but fifteen hands and two inches, which is 62 inches or 157.5 centimetres. The digit after the point runs from 0 to 3 and then rolls over, so 15.3 is followed by 16.0. Anyone converting a list of horse heights with ordinary decimal arithmetic will produce numbers that are wrong by up to three inches.
Where the boundary between pony and horse falls is decided by this measurement. Most classifications put it at 14.2 hands, which is 58 inches or 147.3 centimetres, and competition classes at every level are drawn on the same scale. Because a placing can depend on a fraction of an inch, official measurement is a regulated procedure carried out on a level surface by an approved measurer.
The area form has never followed the length into use. Body-derived units were invented for laying along things, the height of an animal, the length of a cloth, the depth of water, and not for enclosing ground, which is why the acre and the chain came from ploughing rather than from anatomy. A square hand is simply what appears when the rule for forming areas is applied to a unit that had no such purpose.
As a quantity it is easy enough to place. A hundred square centimetres is a large sticky note, a beer mat and a half, or the palm of a hand, which is the same comparison used to estimate burn area in first aid. Sixteen square hands make a square foot, and 2304 of them make a square yard.
One square hand equals 16 square inches, about 103.23 square centimetres, or about 0.0103 square metres.
The square mile is a unit of area equal to 640 acres, or 2.589988 square kilometres. Its symbol is sq mi. It is the area of a square one mile on a side, and it is the unit in which American and British counties, cities, parks and disaster zones are described. Its equivalence to exactly 640 acres is not an accident but the foundation of how much of North America was laid out.
The United States Public Land Survey, begun in 1785, divided the western territories into townships of six miles square, each containing thirty-six sections of one square mile. A section holds 640 acres, a quarter section 160, and a quarter of that 40. Those numbers ran through homestead law, land sales and inheritance for a century, and they are still visible from the air in the grid of roads that follows section lines across the Midwest.
Because the survey made the square mile a legal container rather than a mere measurement, it shaped settlement patterns. A quarter section was considered the amount of land a family could work, so farms across the plains came in multiples of 160 acres, and the mile spacing of section-line roads set how far apart towns, schools and grain elevators could usefully sit.
Today its everyday use is descriptive. Population density in American statistics is people per square mile, so around 92 for the country as a whole against nearly 30,000 for Manhattan. Wildfire extent, flood inundation, national park size and metropolitan area are all reported the same way, and British usage matches it for county and national park areas even where other measurements have gone metric.
Converting is straightforward if the factor is remembered: one square mile is 2.59 square kilometres, and one square kilometre is 0.386 square miles. The relationship is not intuitive because it is the square of the length ratio, so a place described as ten times larger in square miles is only about 3.2 times larger in linear extent.
Its awkwardness shows when the three imperial land units are chained. A square mile is 640 acres, an acre is 4840 square yards, and a square yard is nine square feet, so going from a square mile to a square foot means multiplying by 27,878,400. That figure is exactly why land and building are measured with different units even inside the same system.
One square mile equals 640 acres, about 2.59 square kilometres, 259 hectares, or 27,878,400 square feet.