| Square centimeters (cm²) | Square nautical miles (sq nmi) |
|---|---|
| 1 Square centimeter | 2.91553349598 × 10-11 sq nmi |
| 2 Square centimeters | 5.83106699196 × 10-11 sq nmi |
| 3 Square centimeters | 8.74660048794 × 10-11 sq nmi |
| 4 Square centimeters | 1.16621339839 × 10-10 sq nmi |
| 5 Square centimeters | 1.45776674799 × 10-10 sq nmi |
| 10 Square centimeters | 2.91553349598 × 10-10 sq nmi |
| 20 Square centimeters | 5.83106699196 × 10-10 sq nmi |
| 25 Square centimeters | 7.28883373995 × 10-10 sq nmi |
| 50 Square centimeters | 0.00000000145776674799 sq nmi |
| 100 Square centimeters | 0.00000000291553349598 sq nmi |
| Reference | Square centimeters (cm²) | Square nautical miles (sq nmi) |
|---|---|---|
| A sheet of A4 paper | 623.7 cm² | 0.0000000181842 sq nmi |
| A tennis court | 2608000 cm² | 0.0000760371 sq nmi |
| A football pitch | 71400000 cm² | 0.00208169 sq nmi |
| One hectare | 100000000 cm² | 0.00291553 sq nmi |
| Central Park, New York | 3.41 × 1010 cm² | 0.994197 sq nmi |
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 nautical mile is a unit of area equal to 3,429,904 square metres, or about 3.43 square kilometres. Its symbol is sq nmi. It is the area of a square one nautical mile on a side, the nautical mile being defined as exactly 1852 metres. It is the working unit of everything that happens at sea and is measured across a surface rather than along a line.
Its usefulness comes from the definition of the nautical mile itself. One nautical mile is very nearly one minute of latitude, so a square nautical mile is close to a one-minute cell on a chart. That makes it the natural grid square for anything plotted on a nautical chart, because the unit and the graticule agree without any conversion, and a navigator can read distance and area off the same scale.
Maritime law is written in nautical miles and therefore accounted in square ones. Under the international law of the sea, a coastal state has a territorial sea of twelve nautical miles, a contiguous zone of twenty-four and an exclusive economic zone reaching two hundred. The resulting areas are vast: a state with scattered island possessions can control several million square kilometres of ocean, and comparisons between such claims are usually made after converting these figures to metric.
Search and rescue planning depends on the unit directly. A search area is defined in square nautical miles, and the time to cover it follows from the search vessel's speed in knots and the sweep width of its sensors, both of which are already in nautical units. Keeping the whole calculation in one system is what allows a coordinator to estimate coverage without stopping to convert anything.
Fisheries science and naval operations use it the same way. Fish stock density is reported per square nautical mile, survey transects are spaced in nautical miles, exercise and restricted areas are drawn as blocks of them, and aviation control zones over water are described in the same terms because aircraft also navigate in knots.
For conversion, one square nautical mile is 3.43 square kilometres, 1.32 square statute miles, or about 848 acres. The ratio to the statute mile is not intuitive, since the nautical mile is only about 15 per cent longer but the square is a third larger, which is the usual consequence of squaring a length ratio.
One square nautical mile equals 3,429,904 square metres, about 3.43 square kilometres, about 1.32 square miles, or about 848 acres.