What the area converter does
The area converter changes a value between eleven units of area: square millimeter (mm²), square centimeter (cm²), square meter (m²), square kilometer (km²), hectare (ha), square inch (in²), square foot (ft²), square yard (yd²), acre (ac), square mile (mi²) and the Chinese mu. Type on either side and the opposite field follows; the All Units list shows the same quantity in every unit.
The factors are exact definitions. Every unit reduces to the square meter: a hectare is 10,000 m², the international acre is 4,046.8564224 m² and a square foot is 0.09290304 m². For lengths and volumes, see the length converter and the volume converter; for typed arithmetic, the scientific calculator.
Worked examples
Every readout below comes from this converter.
One acre in the list. 1 ac reads 4,046.8564224 m², 43,560 ft², 4,840 yd², 6,272,640 in², 0.4046856422 ha, 0.0040468564 km² and 0.0015625 mi² — the definitions being 1 acre = 4,840 yd² = 43,560 ft² = 1/640 mi².
Hectares against acres.
| Input |
Readout |
| 1 hectare |
2.4710538147 ac |
| 100 hectares |
247.105381467 ac |
| 1 acre |
0.4046856422 ha |
| 25 acres |
10.117141056 ha |
| 1 mu |
666.666666667 m² |
The mu is the Chinese land unit, fixed at exactly 2000/3 m².
Square feet against square meters. 1 ft² reads 0.09290304 m² and 1,000 ft² read 92.90304 m²; reversed, 1 m² reads 10.7639104167 ft² and 1,000 m² read 10,763.9104167 ft². The two factors are reciprocals. 1 ft² is also 144 in², and 1 in² reads 6.4516 cm², with the reverse reading 0.15500031 in².
A square mile. 1 mi² reads 640 ac, 2,589,988.1103 km², 2,589,988.11034 m², 27,878,400 ft², 258.998811034 ha and 2,589,988,110,340 mm²; the last readout rounds the defined 2,589,988.110336 m².
Where the factors come from
The square meter is the SI unit of area, and prefixes square with the unit: 1 km² is 10⁶ m², 1 cm² is 10⁻⁴ m² and 1 mm² is 10⁻⁶ m². A hectare is a 100 m × 100 m square, 10,000 m², so 100 hectares make one square kilometer.
The imperial units rest on the 1959 international yard of exactly 0.9144 m: the foot is 0.3048 m, the inch 25.4 mm and the mile 1,609.344 m. Squaring gives in² = 6.4516 cm², ft² = 0.09290304 m², yd² = 0.83612736 m² and mi² = 2,589,988.110336 m². The international acre is 4,840 yd² of that yard, 4,046.8564224 m².
Reading results and limits
- Display rule.
- Results keep 12 significant digits and at most 10 decimal places, with thousands separators; zero prints as
0. The two rules interact: 1 acre reads 4,046.8564224 m², 1 square mile reads 2,589,988.11034 m², and 1 hectare reads 2.4710538147 ac — the exact 2.471053814671… stops at the ten-decimal cap. - Extremes.
- At the extremes the shape changes. At 10¹⁵ and above, and below 10⁻¹⁰, results print exponentially with six decimals: 10⁹ km² reads
1.000000e+15 m²; 1 mm² reads 1.000000e-12 km², and in square miles 3.861022e-13 mi². The threshold is strict and the stored value decides a border case: 1 mm² in hectares reads 1.000000e-10 ha, while 1 cm² in square kilometers reads 0.0000000001 km². - Ten-decimal cap at the small end.
- The ten-decimal cap swallows digits at the small end: 1 mm² in acres reads
0.0000000002 ac, while the square-meter row keeps 0.000001 m². Swap carries the displayed value, so a round trip can return rounded text: 1,000 m² → ft² reads 10,763.9104167, and swapping back reads 999.999999999 m²; 1 km² → mi² reads 0.3861021585 and swaps back as 0.9999999999 km².