| Square decimeters (dm²) | Square yards (sq yd) |
|---|---|
| 1 Square decimeter | 0.011959900463 sq yd |
| 2 Square decimeters | 0.023919800926 sq yd |
| 3 Square decimeters | 0.035879701389 sq yd |
| 4 Square decimeters | 0.047839601852 sq yd |
| 5 Square decimeters | 0.0597995023151 sq yd |
| 10 Square decimeters | 0.11959900463 sq yd |
| 20 Square decimeters | 0.23919800926 sq yd |
| 25 Square decimeters | 0.298997511575 sq yd |
| 50 Square decimeters | 0.597995023151 sq yd |
| 100 Square decimeters | 1.1959900463 sq yd |
| Reference | Square decimeters (dm²) | Square yards (sq yd) |
|---|---|---|
| A sheet of A4 paper | 6.237 dm² | 0.0745939 sq yd |
| A tennis court | 26080 dm² | 311.914 sq yd |
| A football pitch | 714000 dm² | 8539.37 sq yd |
| One hectare | 1000000 dm² | 11959.9 sq yd |
| Central Park, New York | 341000000 dm² | 4078326 sq yd |
The square decimetre is a unit of area equal to one hundredth of a square metre, or one hundred square centimetres. It is written dm². It is the area of a square ten centimetres on a side, which is about the size of a palm or a drinks coaster, and it sits in the gap between the square centimetre of small objects and the square metre of rooms.
The decimetre owes its survival to volume rather than to area. A cubic decimetre is exactly one litre, which quietly builds the prefix into the most used volume unit in the world, and a square decimetre is the cross-section of that litre cube. Anyone who can picture a litre carton already knows what a square decimetre looks like: it is the face of the box.
Its one substantial commercial home is the leather trade. Hides are irregular, so they are measured by area rather than by length, and European tanneries, shoe factories and leather goods makers buy and sell in square decimetres. A whole cowhide runs to something like 200 to 250 square decimetres, a lambskin to about 50, and prices, cutting yields and waste allowances are all calculated on that basis. British and American buyers use square feet for the same purpose, and one square foot is 9.29 square decimetres.
Everyday objects land conveniently on it. A sheet of A4 paper is 6.24 square decimetres, a standard floor tile of thirty centimetres is nine, and a large postage stamp is a small fraction of one. Schools use the unit for exactly this reason: it lets a class measure real objects without either very large or very small numbers, and it makes the squaring rule visible, since ten centimetres on a side gives a hundred square centimetres.
Outside those uses it is rare, and for the usual reason. Engineering standardised on prefixes that step by a factor of a thousand, so square millimetres, square metres and square kilometres cover everything in practice. Ten square decimetres is more naturally written as 0.1 square metres, which sorts correctly beside every other figure in a specification.
Converting is straightforward once the squaring is kept in mind. Multiply by a hundred for square centimetres, divide by a hundred for square metres, and remember that the factor between neighbouring units is the square of the factor between the lengths, not the factor itself.
One square decimetre equals 100 square centimetres, 0.01 square metres, or about 15.5 square inches.
The square yard is a unit of area equal to nine square feet, or 0.83612736 square metres exactly. Its symbol is sq yd, sometimes written yd². It is the area of a square one yard on a side, and 4840 of them make an acre. It occupies the awkward middle of the imperial ladder: too large for a workshop, too small for a field, and used mainly for surfaces that are laid rather than built.
Ground coverings are its main business. Turf is sold and laid by the square yard, asphalt paving and road resurfacing are measured in square yards in the United States, and carpet was priced that way for most of the twentieth century before American retailers moved to the square foot. Anything that arrives on a roll or a pallet and is spread out tends to be counted in this unit.
Textiles use it in an indirect but important way. Cloth is bought by the linear yard off a roll of known width, but its weight is specified in ounces per square yard, which is what allows two fabrics of different widths to be compared. A shirting might be four ounces per square yard and a heavy canvas eighteen, and those numbers describe the cloth more usefully than any measurement of the bolt does.
It also carries a large part of the South Asian property market. In Pakistan and northern India, plots are commonly sold in gaz, which is the square yard under a local name, so a house plot might be advertised at 240 gaz. Larger holdings switch to the marla and the kanal, both of which are defined as multiples of the square yard, so the whole regional system rests on this unit even where the English name is never used.
Its relationship to the rest of the imperial ladder is unusually clean at one step and unusually messy at the next. Nine square feet is easy; 1296 square inches and 4840 to the acre are not. That mixture is characteristic of a system built from body measures and ploughing practice rather than from a single decimal idea.
Conversion to metric is exact but not memorable: one square yard is 0.83612736 square metres and one square metre is 1.19599 square yards. A rough rule that a square metre is about a fifth larger than a square yard is close enough for judging a room, though not for ordering material.
One square yard equals 9 square feet, 1296 square inches, about 0.8361 square metres, or about 0.000207 acres.