Square metric area unit.
Square Kilometers to Acres Converter — km2 to ac
Convert Square Kilometer (km2) to Acre (ac) using the exact conversion factor (1 square kilometer = 247.1053815 acre). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
Square Kilometers to Acres converter
Converter
Agriculture Converter
Convert acres, hectares, yield, seed, fertilizer, irrigation, and application-rate units.
Context values
Some unit families need one extra value for a physically accurate result.
An international acre is 4,046.8564224 square meters.
Result = input x 1e+6 / 4046.856422.
Area units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Square Kilometers to Acres
Square Kilometer and Acre both measure a farming-related quantity — a land area or an application/yield rate per unit area — used to report crop yields, calculate how much fertilizer or seed a field needs, and plan irrigation. Square Kilometer is typically associated with used worldwide for city, region, and country-scale area reporting., while Acre is typically associated with united States.
Formula
acres = square kilometers × 247.105381467
This factor comes from each unit's defined relationship to the category's base unit: 1 square kilometer equals 1000000 base units, and 1 acre equals 4046.8564224 base units, so dividing one by the other gives the direct square kilometer-to-acre factor of 247.105381467.
Simple example
1 km2 × 247.1053815 = 247.1053815 ac
1 square kilometer = 247.1053815 acres.
Real-world example
100 km2 × 247.1053815 = 24,710.53815 ac
100 square kilometers = 24,710.53815 acres.
Conversion table
| Square Kilometer (km2) | Acre (ac) |
|---|---|
| 1 km2 | 247.1053815 ac |
| 5 km2 | 1,235.526907 ac |
| 10 km2 | 2,471.053815 ac |
| 50 km2 | 12,355.26907 ac |
| 100 km2 | 24,710.53815 ac |
| 500 km2 | 123,552.6907 ac |
Reverse conversion: Acre to Square Kilometer
247.1053815 ac × 0.004046856422 = 1 km2
247.1053815 acres = 1 square kilometers.
square kilometers = acres × 0.0040468564224
For a page dedicated to this direction, see Acre to Square Kilometer.
Square Kilometer vs. Acre
| Aspect | Square Kilometer | Acre |
|---|---|---|
| Family | SI derived (metric prefix) unit | US/imperial customary unit |
| Typical use | National and regional land-area statistics | Measuring farmland, ranch, and rural property size in the US |
| Where it's used | Used worldwide for city, region, and country-scale area reporting. | United States |
Understanding the Square Kilometer
Square Kilometer (km2) measures area. A square kilometer is one million square meters — the area of a 1 km × 1 km square. It is classified as a SI derived (metric prefix) unit.
Where it's used: Used worldwide for city, region, and country-scale area reporting.
Uses of the Square Kilometer today
- National and regional land-area statistics
- City and urban planning at large scale
- Geography and cartography
History of the Square Kilometer
Like other metric-prefixed area units, the square kilometer follows automatically from the kilometer once the meter was standardized in the 1790s French metric reform.
Historical origin. Square Kilometer was not the invention of a single named person; it developed through the process described above.
Understanding the Acre
Acre (ac) measures area. The international acre is defined as exactly 4,046.8564224 square meters. It is classified as a US/imperial customary unit.
Where it's used: United States United Kingdom (informal/historical, land registry legacy) Countries with historical British land-survey systems
International acre vs. US survey acre. The US survey acre, based on the US survey foot, differs from the international acre by about two parts per million. The US retired the survey foot/acre for federal use at the end of 2022.
Uses of the Acre today
- Measuring farmland, ranch, and rural property size in the US
- Real estate listings and zoning for land parcels
- Forestry and land-management reporting
History of the Acre
The acre originated in medieval England as a practical field measurement: the area a yoke of oxen could plow in one day, roughly a furlong (660 ft) long by a chain (66 ft) wide, giving the 43,560 square feet still used today.
Edward I's 1305 statute formalized this figure. In 1959, the same International Yard and Pound Agreement that fixed the pound also fixed the international acre at exactly 4,046.8564224 m², though the US separately retained a slightly different 'US survey acre' for some legacy land records until it was phased out in 2023.
Historical origin. Acre was not the invention of a single named person; it developed through the process described above.
Square Kilometer — sources
- BIPM SI Brochure — Coherent derived units — Basis for metric-prefixed area units.
Acre — sources
- NIST — US Survey Foot: Revised Unit Conversion Factors — Documents the 1959 international acre definition and the 2022/2023 survey-foot retirement.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many acres are in 1 square kilometer?
1 square kilometer equals 247.1053815 acres, using the exact defined conversion factor rather than an estimate.
How do I convert square kilometer to acre?
Multiply the square kilometer value by 247.1053815. The converter above does this instantly to whatever precision you set.
How do I convert acre back to square kilometer?
Use the reverse factor: 1 acre equals 0.0040468564 square kilometers. You can also use the swap control in the converter above to flip the direction instantly.
What is a square kilometer?
Square Kilometer (km2) measures area. A square kilometer is one million square meters — the area of a 1 km × 1 km square. It is classified as a SI derived (metric prefix) unit.
What is a acre?
Acre (ac) measures area. The international acre is defined as exactly 4,046.8564224 square meters. It is classified as a US/imperial customary unit.
Is the square kilometer to acre conversion exact?
Yes. The international acre is defined as exactly 4,046.8564224 square meters. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
What is the difference between international acre vs. us survey acre?
The US survey acre, based on the US survey foot, differs from the international acre by about two parts per million. The US retired the survey foot/acre for federal use at the end of 2022.
Where is the square kilometer still used today?
Used worldwide for city, region, and country-scale area reporting.