| Square meters (m²) | Square chains (sq ch) |
|---|---|
| 1 Square meter | 0.00247105381467 sq ch |
| 2 Square meters | 0.00494210762934 sq ch |
| 3 Square meters | 0.00741316144401 sq ch |
| 4 Square meters | 0.00988421525869 sq ch |
| 5 Square meters | 0.0123552690734 sq ch |
| 10 Square meters | 0.0247105381467 sq ch |
| 20 Square meters | 0.0494210762934 sq ch |
| 25 Square meters | 0.0617763453668 sq ch |
| 50 Square meters | 0.123552690734 sq ch |
| 100 Square meters | 0.247105381467 sq ch |
| Reference | Square meters (m²) | Square chains (sq ch) |
|---|---|---|
| A sheet of A4 paper | 0.06237 m² | 0.00015412 sq ch |
| A tennis court | 260.8 m² | 0.644451 sq ch |
| A football pitch | 7140 m² | 17.6433 sq ch |
| One hectare | 10000 m² | 24.7105 sq ch |
| Central Park, New York | 3410000 m² | 8426.29 sq ch |
The square metre is the SI unit of area, written m². It is the area of a square whose sides each measure one metre, and because the metre is a base unit, every other area unit in the system is derived from it by squaring a length. It is the unit in which most of the world buys homes, specifies materials and describes land.
Property is its largest everyday use. Outside the United States and, in part, the United Kingdom, dwellings are advertised, taxed and compared by their floor area in square metres, and price per square metre is the standard way of comparing one district with another. A modest one-bedroom flat runs to about 45 square metres, a family house between 100 and 150, and a single parking space takes up roughly 12.5.
Materials are sold and specified by the square metre because coverage, not volume, is what a builder needs to know. A litre of emulsion paint covers about ten square metres, floor tiles and laminate are priced by the square metre, and insulation is rated by its thermal resistance per square metre. Paper carries its own version of the same idea: the weight of a sheet stock is given in grams per square metre, so 80 g/m² office paper and 300 g/m² card are compared on one scale.
Physics uses the square metre as the denominator of almost every flux. Solar irradiance at the earth's surface peaks near 1000 watts per square metre, which is the figure solar panels are rated against. Pressure is force per square metre, and one newton per square metre is one pascal by definition. Heat loss through a wall is quoted in watts per square metre per kelvin, and sound intensity in watts per square metre.
Medicine uses it for the human body. An adult's skin covers between 1.6 and 2.0 square metres, and that figure is calculated for each patient before chemotherapy, because many drug doses are prescribed in milligrams per square metre rather than per kilogram. Burn severity is assessed as the percentage of body surface affected, using the same underlying measurement.
Where imperial units survive, the square foot competes directly with it. American and British commercial property is still let by the square foot, and one square metre is 10.76 square feet, which is why converted figures rarely come out round. Land at a larger scale moves to the hectare, equal to 10,000 square metres, and then to the square kilometre.
One square metre equals 10,000 square centimetres, about 10.764 square feet, about 1.196 square yards, or 0.0001 hectares.
The square chain is a unit of area equal to 484 square yards, or 404.686 square metres. Its symbol is sq ch. It is the area of a square one chain on a side, a chain being 22 yards, and ten square chains make exactly one acre. That last relationship is the entire reason the unit exists.
The chain was invented by the English mathematician Edmund Gunter around 1620, and it was a physical object before it was a measurement: a steel chain of one hundred links, 22 yards long, that two people carried across a field. Its length was chosen so that ten square chains would be an acre and eighty chains would be a mile, which let a surveyor work in whole numbers and reach acres by shifting a decimal point.
That was a genuine achievement in an age before decimal calculation. Measurements taken in chains and links could be multiplied together and divided by ten to give acres directly, without the awkward factors of 4840 or 43,560 that the yard and the foot force on the same problem. For three centuries almost every land survey in Britain, Ireland, North America and the colonies was recorded this way.
The consequences outlived the tool. American public land records are written in chains, so deeds and plats still describe boundaries as so many chains and links, and anyone tracing an old title has to convert. Wildland firefighting in the United States measures fire line and fire perimeter in chains to this day, because the unit was already embedded in forestry practice when the agencies were formed.
One familiar object preserves the length exactly. A cricket pitch is one chain from wicket to wicket, twenty-two yards, which is why that number appears in the laws of the game and nowhere else in modern sport. Anyone who can picture a cricket pitch can picture a chain, and a square chain is that length squared, roughly a tenth of an acre or a large suburban garden.
For conversion, the useful facts are that ten square chains make an acre and that one square chain is about 405 square metres, so a hectare is nearly twenty-five square chains. Old surveys quoting areas in chains convert cleanly to acres and only awkwardly to metric, which is a good reason to do the acre step first.
One square chain equals 484 square yards, 0.1 acres, about 404.686 square metres, or about 0.0405 hectares.