How to Convert Acres to Square kilometres (ac to km²)
Area conversions are everyday maths in Singapore property: HDB flats are listed in square metres while condo listings and PSF prices use square feet. This guide shows how to convert acres into square kilometres by hand, with examples and a quick-reference table.
The conversion
To convert acres to square kilometres, multiply the value by 0.0040468564. To go the other way, divide by the same number (or multiply by 247.1053814672). For a quick estimate, multiply by about 0.004.
Square kilometres = acres × 0.0040468564
Worked examples
- 3 ac = 0.012141 km²
- 12.5 ac = 0.050586 km²
- 75 ac = 0.303514 km²
Acres to Square kilometres table
| Acres | Square kilometres |
|---|---|
| 1 ac | 0.004047 km² |
| 2 ac | 0.008094 km² |
| 5 ac | 0.020234 km² |
| 10 ac | 0.040469 km² |
| 20 ac | 0.080937 km² |
| 25 ac | 0.101171 km² |
| 50 ac | 0.202343 km² |
| 100 ac | 0.404686 km² |
| 250 ac | 1.0117 km² |
| 500 ac | 2.0234 km² |
| 1,000 ac | 4.0469 km² |
Common questions
Is ac to km² exact?
The factors used here are the internationally defined values where they exist; results are rounded for display only.
How do I convert back?
Use the Square kilometres to Acres converter.
Mistakes to avoid
Multiplying when you should divide
Converting to a smaller unit gives a bigger number, and converting to a larger unit gives a smaller one. If your answer moves the wrong way, you have inverted the factor.
Mixing similar-sounding units
US and imperial gallons, pints and tons are different sizes, and decimal kilobytes differ from binary kibibytes.
Rounding the factor too early
Using 3 instead of 3.28 for feet per metre introduces an error of almost 9% before you have started.
Background
A conversion table is handy for common values, but a calculator is faster and avoids interpolation errors for anything in between.
Singapore adopted the metric system in the 1970s, replacing imperial units and traditional Chinese measures in most official uses. Metric units are now standard in schools, trade and government, but older units survive in property, markets and imported goods.
For everyday use, three or four significant figures are usually enough. Engineering, science and trade documents may need more, and rounding should happen only at the end of a calculation.
For any value, use the Acres to Square kilometres Converter or browse all area converters.
Run your own numbers: Acres to Square kilometres Converter