Square meter (m²)

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.

Square meter conversion table