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.
| Unit | Symbol | 1 Square hand equals | 1 of these equals | Converter |
|---|---|---|---|---|
| Square millimeter | mm² | 10322.56 mm² | 0.0000968751937504 sq hh | Square hands to Square millimeters |
| Square centimeter | cm² | 103.2256 cm² | 0.00968751937504 sq hh | Square hands to Square centimeters |
| Square decimeter | dm² | 1.032256 dm² | 0.968751937504 sq hh | Square hands to Square decimeters |
| Square meter | m² | 0.01032256 m² | 96.8751937504 sq hh | Square hands to Square meters |
| Square decameter | dam² | 0.0001032256 dam² | 9687.51937504 sq hh | Square hands to Square decameters |
| Square hectometer | hm² | 0.000001032256 hm² | 968751.937504 sq hh | Square hands to Square hectometers |
| Square kilometer | km² | 0.00000001032256 km² | 96875193.7504 sq hh | Square hands to Square kilometers |
| Centiare | ca | 0.01032256 ca | 96.8751937504 sq hh | Square hands to Centiares |
| Deciare | da | 0.001032256 da | 968.751937504 sq hh | Square hands to Deciares |
| Are | a | 0.0001032256 a | 9687.51937504 sq hh | Square hands to Ares |
| Decare | daa | 0.00001032256 daa | 96875.1937504 sq hh | Square hands to Decares |
| Hectare | ha | 0.000001032256 ha | 968751.937504 sq hh | Square hands to Hectares |
| Square inch | sq in | 16 sq in | 0.0625 sq hh | Square hands to Square inches |
| Square foot | sq ft | 0.111111111111 sq ft | 9 sq hh | Square hands to Square feet |
| Square yard | sq yd | 0.0123456790123 sq yd | 81 sq hh | Square hands to Square yards |
| Square chain | sq ch | 0.0000255076012652 sq ch | 39204 sq hh | Square hands to Square chains |
| Acre | ac | 0.00000255076012652 ac | 392040 sq hh | Square hands to Acres |
| Square furlong | sq fur | 0.000000255076012652 sq fur | 3920400 sq hh | Square hands to Square furlongs |
| Square mile | sq mi | 0.00000000398556269768 sq mi | 250905600 sq hh | Square hands to Square miles |
| Square nautical mile | sq nmi | 0.00000000300957694443 sq nmi | 332272614.545 sq hh | Square hands to Square nautical miles |
| Square league | sq lea | 4.42840299743 × 10-10 sq lea | 2258150400 sq hh | Square hands to Square leagues |