Area conversions are squared length conversions, which is where the intuition breaks. Doubling a room's dimensions quadruples its floor area. A square metre is not 100 square centimetres — it is 10,000, because both sides scale.
Every factor below follows from the length definitions: a square inch is exactly 0.00064516 m² because an inch is exactly 0.0254 m, and squaring an exact number gives another exact number.
Quick reference
The table follows whichever units you select above.
Land units, which are the awkward ones
An acre is 43,560 square feet. That number looks arbitrary because it is historical: an acre was a chain (66 ft) by a furlong (660 ft), the area a man with an ox was reckoned to plough in a day. A square mile holds exactly 640 acres, which is why American land parcels are so often quartered and re-quartered into 160, 80 and 40-acre lots.
A hectare is far tidier — 10,000 m², a square 100 m on a side. One hectare is about 2.47 acres. For rough conversion, take the hectares and multiply by two and a half.
| Unit | Equals | Rough feel |
|---|---|---|
| 1 acre | 4,046.86 m² | About 60% of a football pitch |
| 1 hectare | 10,000 m² | About 1.4 football pitches |
| 1 square mile | 640 acres | 259 hectares |
Where people go wrong
Squaring the linear factor, or forgetting to
To convert metres to feet you multiply by 3.28084. To convert square metres to square feet you multiply by 3.28084 squared, which is 10.7639. Using the linear factor on an area is the single most common error here, and it makes rooms look three times smaller than they are.
Square feet versus feet square
"Ten square feet" is an area of 10 ft². "Ten feet square" is a square measuring ten feet on each side, which is 100 ft². Ten times larger, and the phrases are one word apart.
Property listings are not consistent. Whether a floor area includes balconies, garages, shared walls or unusable roof space varies by country and sometimes by agent. Converting the number precisely does not make it comparable — check what was measured before comparing two listings.
Common questions
How many square feet in a square metre?
About 10.7639. For rough work, multiply square metres by 10 and add 8 per cent.
How big is an acre?
4,046.86 m², or 43,560 ft². If it were a square it would be about 63.6 m on each side, though acres are historically long and narrow rather than square.
How many acres in a hectare?
About 2.471. Going the other way, an acre is about 0.405 hectares.