Why square units trip people up
A square foot is not 0.3048 square meters. To convert an area you multiply by the square of the length factor: 1 ft = 0.3048 m, so 1 ft² = 0.3048 × 0.3048 = 0.09290304 m². The same goes the other way: 1 m is 3.28 ft, but 1 m² is 10.7639 ft², more than ten times as much.
Said aloud, "square feet" and "feet square" are different things. A room that is "10 square feet" is 10 ft², about 3.2 ft on each side. A room that is "10 feet square" is 10 ft by 10 ft, which is 100 ft². Always check which one a figure means.
If you have the length and width of a room, multiply them first and then convert once. 12 ft × 15 ft is 180 ft², which is 16.72 m². That avoids rounding the two sides separately.
Acres, hectares and square miles
- The acre is exactly 43,560 square feet, which is 4,840 square yards and 4,046.8564224 m². It is used for land in the US and, informally, in the UK.
- The hectare is exactly 10,000 m², a square 100 m on each side. It is 2.4710538 acres. Land is measured in hectares in most of the world.
- The square mile is exactly 640 acres, and is 2.589988 km² or 258.999 ha.
- The square kilometer is 100 hectares, or 1,000,000 m².
For a feel of the sizes: an acre is a little smaller than an American football field without its end zones (about 91 percent of it), and a hectare is about 40 percent bigger than a soccer pitch of 105 by 68 m, which is 7,140 m² or 0.714 ha.
A few familiar areas
- An Olympic swimming pool is 50 m by 25 m, which is 1,250 m² or 13,455 ft².
- A doubles tennis court is 78 ft by 36 ft, which is 2,808 ft² or 260.87 m².
- A parking space is often around 2.5 m by 5 m, which is 12.5 m² or 134.5 ft². Sizes vary by place.
- A sheet of US letter paper is 8.5 in by 11 in, which is 93.5 in² or 603.2 cm².
For the conversion people look up most, see square feet to square meters.