| Square hectometers (hm²) | Square hands (sq hh) |
|---|---|
| 1 Square hectometer | 968751.937504 sq hh |
| 2 Square hectometers | 1937503.87501 sq hh |
| 3 Square hectometers | 2906255.81251 sq hh |
| 4 Square hectometers | 3875007.75002 sq hh |
| 5 Square hectometers | 4843759.68752 sq hh |
| 10 Square hectometers | 9687519.37504 sq hh |
| 20 Square hectometers | 19375038.7501 sq hh |
| 25 Square hectometers | 24218798.4376 sq hh |
| 50 Square hectometers | 48437596.8752 sq hh |
| 100 Square hectometers | 96875193.7504 sq hh |
| Reference | Square hectometers (hm²) | Square hands (sq hh) |
|---|---|---|
| A sheet of A4 paper | 0.000006237 hm² | 6.04211 sq hh |
| A tennis court | 0.02608 hm² | 25265.1 sq hh |
| A football pitch | 0.714 hm² | 691689 sq hh |
| One hectare | 1 hm² | 968752 sq hh |
| Central Park, New York | 341 hm² | 330344411 sq hh |
The square hectometre is a unit of area equal to ten thousand square metres. It is written hm², and it is the area of a square one hundred metres on a side, since a hectometre is one hundred metres. It is exactly one hectare, and the two names describe the same quantity by two different routes.
The routes are worth distinguishing. The hectare is built by putting the prefix hecto in front of the are, so it is a hundred ares. The square hectometre is built by squaring a prefixed length, which is how the International System forms every derived area. The second construction is the strictly coherent one; the first is the one written on every land title in the world.
That difference explains where each name is found. Hectare appears in agriculture, forestry, planning, taxation and international statistics. Square hectometre appears mainly in technical and cartographic work in Spanish-speaking countries, where the hectometre is a familiar prefixed length for other reasons, and in documents where an author has chosen to keep every unit inside strict SI form.
The related cubic form is genuinely common in one field. Spanish and Latin American hydrology reports reservoir capacity and river flow in cubic hectometres, a cubic hectometre being one million cubic metres, so a reservoir holding 500 hm³ is holding half a cubic kilometre of water. Readers used to seeing hm in that context find hm² unremarkable, which is much of why the form survives there and almost nowhere else.
For scale, ten thousand square metres is a square one hundred metres on a side. That is about one and a half association football pitches, a large city block, or a good-sized field. It is the largest area that can still be walked around comfortably in a couple of minutes, and it is where land measurement stops being architectural and starts being agricultural.
When converting, the two names need no arithmetic between them: one square hectometre is one hectare exactly. Going further, multiply by ten thousand for square metres or divide by a hundred for square kilometres, and remember that the imperial comparison, 2.471 acres, is the same for both names.
One square hectometre equals 10,000 square metres, 1 hectare, 0.01 square kilometres, or about 2.471 acres.
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.