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Area
Acres to Square kilometers
Convert acres (ac) to square kilometers (km²). Type a value below to see the result update instantly. Reference table and formula included.
Calculator
1 ac = 0.004047 km²
Acres to Square kilometers Conversion Table
Common values, ready to copy:
| acres | square kilometers |
|---|---|
| 1 ac | 0.004047 km² |
| 2 ac | 0.008094 km² |
| 5 ac | 0.020234 km² |
| 10 ac | 0.040469 km² |
| 25 ac | 0.101171 km² |
| 50 ac | 0.202343 km² |
| 100 ac | 0.404686 km² |
| 1,000 ac | 4.0469 km² |
Formula
square kilometers = acres × 0.00404686
Area conversions are derived from length: 1 ft² = (0.3048 m)² = 0.092903 m². 1 acre = 4,046.86 m². 1 hectare = 10,000 m² exactly.
About Acres and Square kilometers
Acres (ac): An old English unit, originally the area a yoke of oxen could plow in a day; standardized at exactly 4,046.86 m² (43,560 sq ft). Common uses: Land area in the US, UK, and most former British colonies — farm sizes, residential lots, and ranch acreage.
Square kilometers (km²): One kilometer squared, or one million square meters. Common uses: City area, national park sizes, agricultural land, and geographic features at the regional scale.
How the conversion works
Area conversions are derived from length: 1 ft² = (0.3048 m)² = 0.092903 m². 1 acre = 4,046.86 m². 1 hectare = 10,000 m² exactly.
The exact relationship is square kilometers = acres × 0.00404686, which the calculator at the top of this page applies in both directions. Type into either field and the other updates immediately.
When this conversion matters
Converting between acres and square kilometers comes up wherever area measurements move between systems — from one country's conventions to another's, from a scientific reference to a practical specification, or from one industry's working unit to another's. The calculator and reference table above cover the everyday range; for unusual values you can type any number into either field.