| Square centimeters (cm²) | Square yards (sq yd) |
|---|---|
| 1 Square centimeter | 0.00011959900463 sq yd |
| 2 Square centimeters | 0.00023919800926 sq yd |
| 3 Square centimeters | 0.00035879701389 sq yd |
| 4 Square centimeters | 0.00047839601852 sq yd |
| 5 Square centimeters | 0.000597995023151 sq yd |
| 10 Square centimeters | 0.0011959900463 sq yd |
| 20 Square centimeters | 0.0023919800926 sq yd |
| 25 Square centimeters | 0.00298997511575 sq yd |
| 50 Square centimeters | 0.00597995023151 sq yd |
| 100 Square centimeters | 0.011959900463 sq yd |
| Reference | Square centimeters (cm²) | Square yards (sq yd) |
|---|---|---|
| A sheet of A4 paper | 623.7 cm² | 0.0745939 sq yd |
| A tennis court | 2608000 cm² | 311.914 sq yd |
| A football pitch | 71400000 cm² | 8539.37 sq yd |
| One hectare | 100000000 cm² | 11959.9 sq yd |
| Central Park, New York | 3.41 × 1010 cm² | 4078326 sq yd |
The square centimetre is a unit of area equal to one ten-thousandth of a square metre, written cm². It is the area of a square one centimetre on a side, and it contains one hundred square millimetres. It is the working unit for anything the size of a hand or smaller: wounds, printed circuits, laboratory cultures, sensor chips and postage stamps.
The arithmetic catches people out. Because area scales with the square of length, one hundred square centimetres make a square decimetre and ten thousand make a square metre, not one hundred. A square ten centimetres on a side is 100 cm², and doubling its side to twenty centimetres gives 400 cm², not 200. Nearly every mistake made with this unit comes from applying the linear factor instead of the squared one.
Medicine measures skin in it. Wounds, ulcers, burns and skin lesions are recorded in square centimetres so that healing can be tracked as a shrinking number over weeks, and dermatological treatments are dosed by the area treated. A typical adult palm covers roughly 100 square centimetres, which is why the palm is used as a rough field estimate of burn extent.
Laboratories rely on it for cell culture. Flasks are named by their growth surface, so a T25 offers 25 square centimetres and a T75 offers 75, and cell densities are counted per square centimetre. Photovoltaic research reports efficiency on cells of exactly one square centimetre, precisely so that results from different laboratories describe the same thing.
Engineering uses it for pressure in some traditions. The kilogram-force per square centimetre, close to one atmosphere, is still printed on tyre gauges, pressure vessels and hydraulic equipment in Japan, Korea and parts of eastern Europe, and it survives because the number it produces is conveniently near the values people already knew. Printed circuit boards are quoted and priced by the square centimetre for the same practical reason.
Against the imperial system it faces the square inch, which is 6.4516 square centimetres exactly. That factor comes straight from the inch being defined as exactly 2.54 centimetres, so unlike most imperial conversions this one is not an approximation, merely an awkward number.
One square centimetre equals 100 square millimetres, 0.0001 square metres, or about 0.155 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.