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.
| Unit | Symbol | 1 Square centimeter equals | 1 of these equals | Converter |
|---|---|---|---|---|
| Square millimeter | mm² | 100 mm² | 0.01 cm² | Square centimeters to Square millimeters |
| Square decimeter | dm² | 0.01 dm² | 100 cm² | Square centimeters to Square decimeters |
| Square meter | m² | 0.0001 m² | 10000 cm² | Square centimeters to Square meters |
| Square decameter | dam² | 0.000001 dam² | 1000000 cm² | Square centimeters to Square decameters |
| Square hectometer | hm² | 0.00000001 hm² | 100000000 cm² | Square centimeters to Square hectometers |
| Square kilometer | km² | 1 × 10-10 km² | 10000000000 cm² | Square centimeters to Square kilometers |
| Centiare | ca | 0.0001 ca | 10000 cm² | Square centimeters to Centiares |
| Deciare | da | 0.00001 da | 100000 cm² | Square centimeters to Deciares |
| Are | a | 0.000001 a | 1000000 cm² | Square centimeters to Ares |
| Decare | daa | 0.0000001 daa | 10000000 cm² | Square centimeters to Decares |
| Hectare | ha | 0.00000001 ha | 100000000 cm² | Square centimeters to Hectares |
| Square inch | sq in | 0.155000310001 sq in | 6.4516 cm² | Square centimeters to Square inches |
| Square hand | sq hh | 0.00968751937504 sq hh | 103.2256 cm² | Square centimeters to Square hands |
| Square foot | sq ft | 0.00107639104167 sq ft | 929.0304 cm² | Square centimeters to Square feet |
| Square yard | sq yd | 0.00011959900463 sq yd | 8361.2736 cm² | Square centimeters to Square yards |
| Square chain | sq ch | 0.000000247105381467 sq ch | 4046856.4224 cm² | Square centimeters to Square chains |
| Acre | ac | 0.0000000247105381467 ac | 40468564.224 cm² | Square centimeters to Acres |
| Square furlong | sq fur | 0.00000000247105381467 sq fur | 404685642.24 cm² | Square centimeters to Square furlongs |
| Square mile | sq mi | 3.86102158542 × 10-11 sq mi | 25899881103.4 cm² | Square centimeters to Square miles |
| Square nautical mile | sq nmi | 2.91553349598 × 10-11 sq nmi | 34299040000 cm² | Square centimeters to Square nautical miles |
| Square league | sq lea | 4.2900239838 × 10-12 sq lea | 233098929930 cm² | Square centimeters to Square leagues |