Area units and their equivalents
| Unit | Symbol | In square meters |
|---|---|---|
| Square kilometer | km² | 1,000,000 m² |
| Hectare | ha | 10,000 m² |
| Are | a | 100 m² |
| Square meter | m² | 1 m²base unit |
| Square centimeter | cm² | 0.0001 m² |
| Square mile | mi² | 2,589,988 m² |
| Acre | ac | 4,047 m² |
| Square foot | ft² | 0.092903 m² |
| Square inch | in² | 0.00064516 m² |
| Square yard | yd² | 0.836127 m² |
| Square millimeter | mm² | 0.000001 m² |
Frequently asked questions
Why not multiply by the same factor as lengths?
Because an area has two dimensions: both length AND width are converted. The factor therefore applies twice, giving its square. Multiplying square meters by 3.28 instead of 10.76 understates the area threefold.
Hectare or acre?
The hectare (10,000 m², a square 100 m on each side) is the European farming unit; the acre (4,047 m²) dominates in the US and UK. One hectare is about 2.47 acres.
How do you convert a floor area into a roof area?
Divide by the cosine of the slope, and never add the percentage from the quote. A 30 % pitch, common on a house, is 16.7° and adds only 4.4 %: 100 m² of footprint becomes 104.4 m² of covering. A 30° pitch adds 15.5 %, and a 45° roof adds 41.4 %. Mixing up degrees and percent is what leaves a job one pallet of tiles short. North American roofers count in squares of 100 square feet, or 9.29 m² each.
Which land units are used in India?
Units that change from one state to the next, and no listing says which one it means. The bigha is about 2,529 m² in Uttar Pradesh and Bihar, 1,337.8 m² in West Bengal and Assam, and Rajasthan keeps two of them, the pucca at 2,529 m² and the kaccha at 1,618 m². Below it come the katha, one twentieth of a bigha, the guntha at 101.17 m² or one fortieth of an acre, the cent at 40.47 m² in Tamil Nadu and Kerala, and the ground at 223 m² in Chennai. Only the square meter and the acre carry legal weight on a deed.
Is a 27-inch screen 12 % bigger than a 24-inch one?
No, it gives 27 % more surface. The diagonal is a length, the area is a square: in 16:9, going from 24 to 27 inches takes the panel from 1,589 to 2,010 cm². Shape matters as much as the diagonal, since a 27-inch in the squarer 4:3 ratio would reach 2,258 cm². The same arithmetic rules pizzas: a 40 cm pizza is not two 20 cm ones, it is four.
The are vanished, the hectare survived it
The are is one hundred square metres and is used nowhere under that name. It survives through its prefixes: the hectare is one hundred ares, that is ten thousand square metres, and the centiare is one hundredth of an are, exactly one square metre, a word French and Belgian deeds still spell out. The acre keeps the trace of its farming origin: one chain of sixty-six feet by one furlong of six hundred and sixty, what a team of oxen ploughed in a day, that is 43,560 square feet or 4,046.8564224 square metres.
The United States surveyed its land for two centuries with a foot that was not the international foot. The survey foot was 1200/3937 of a metre, two parts per million longer than the official 0.3048 metre. The gap looks like nothing and is not nothing across a territory: over the ten kilometres of a township it reaches two centimetres, enough to move a boundary marker. The survey foot was retired on 31 December 2022, and every American cadastral measurement now refers to the international foot.