The units of area
Area units are length units squared, which is the single fact that causes most of the errors. Because the factor is squared, small differences in length become large differences in area: a metre is 3.28 feet, but a square metre is 10.76 square feet. The hectare and the acre are the two units used for land, and they are not close to each other: an acre is about 0.4 hectares.
| Unit | Symbol | Equals |
|---|---|---|
| Square centimetres | cm² | 0.0001 m² |
| Square metres | m² | 1 m² |
| Square kilometres | km² | 1,000,000 m² |
| Hectares | ha | 10,000 m² |
| Ares | a | 100 m² |
| Square feet | ft² | 0.09290304 m² |
| Square inches | in² | 0.00064516 m² |
| Square yards | yd² | 0.83612736 m² |
| Acres | acre | 4,046.8564224 m² |
How to convert by hand
Every area conversion follows the same procedure: take the amount to the base unit, then from there to the target unit. In practice it is a single multiplication, because the two steps combine into one factor.
Square the length factor. To go from square metres to square feet, multiply by 3.28084², which is 10.7639. For land, remember that a hectare is exactly 10,000 m² and an acre is 4,046.86 m².
The equivalents people look up most
| Conversion | Result |
|---|---|
| A one-bedroom flat | 50 m² · 538 ft² |
| A tennis court | 261 m² · 2,808 ft² |
| A football pitch | 7,140 m² · 0.71 ha · 1.76 acres |
| A hectare | 10,000 m² · 2.47 acres |
| An A4 sheet | 0.062 m² · 0.67 ft² |
Common mistakes
- Using the length factor instead of its square. Multiplying by 3.28 instead of 10.76 gives an answer a third of the real one.
- Assuming an acre and a hectare are similar. A hectare is nearly two and a half acres.
- Confusing an “are” with an acre. An are is 100 m², an acre is 4,046.86 m², and the names are a historical accident.
- Converting the sides of a room separately and then multiplying. It works, but it invites rounding errors; convert the area once instead.