Acres to Square Kilometers Converter
Convert acres to square kilometers — 247.1 acres to the square kilometer. Results update as you type; exact factors shown.
One acre is 0.004 square kilometers — see the exact factor, not a rounded rule of thumb.
How the acres to square kilometers converter works
Areas convert through the square meter. Because the inch is exactly 25.4 mm, a square foot is exactly 0.09290304 m², an acre (43,560 square feet) is exactly 4,046.8564224 m² and a square mile (640 acres) is 2,589,988.110336 m². A hectare is 10,000 m² by definition.
The US uses customary units (US gallon, short ton, °F) in daily life; NIST SP 811 gives the exact SI factors.
Common area conversions
| From | To | Units |
|---|---|---|
| 1 ac | 0.004 km² | acre to square kilometers |
| 10 ac | 0.0405 km² | acres to square kilometers |
| 50 ac | 0.2023 km² | acres to square kilometers |
| 100 ac | 0.4047 km² | acres to square kilometers |
| 247.105 ac | 1 km² | acres to square kilometers |
| 500 ac | 2.0234 km² | acres to square kilometers |
| 640 ac | 2.59 km² | acres to square kilometers |
| 1,000 ac | 4.0469 km² | acres to square kilometers |
| 2,500 ac | 10.1171 km² | acres to square kilometers |
| 5,000 ac | 20.2343 km² | acres to square kilometers |
| 10,000 ac | 40.4686 km² | acres to square kilometers |
| 100,000 ac | 404.6856 km² | acres to square kilometers |
Units in this converter and their exact factors
| Unit | Symbol | One unit in square meters |
|---|---|---|
| square millimeter | mm² | 0.000001 square meter |
| square centimeter | cm² | 0.0001 square meter |
| square meter | m² | 1 square meter |
| hectare | ha | 10,000 square meter |
| square kilometer | km² | 1,000,000 square meter |
| square inch | in² | 0.00064516 square meter |
| square foot | ft² | 0.09290304 square meter |
| square yard | yd² | 0.83612736 square meter |
| acre | ac | 4,046.8564224 square meter |
| square mile | mi² | 2,589,988.110336 square meter |
FAQFrequently asked questions about area conversion
How many acres in a square kilometer?
247.105 acres.
What is 640 acres?
One square mile, which is 2.59 km².
What is an acre in square meters?
4,046.86 m².
Why 640 acres to a square mile?
The US Public Land Survey divided townships into square-mile sections of 640 acres, which quarter neatly into 160-acre homesteads.
What is 100 acres in km²?
0.405 km².
Where these figures come from
- BIPM — The International System of Units (SI Brochure, 9th edition) — definitions of the base and derived units.
- NIST Special Publication 811 — Guide for the Use of the International System of Units — the exact conversion factors used here.
- National Institute of Standards and Technology (NIST) — United States's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.