How to convert ac to km²
km² = ac × 0.004046856422. The scale factor is the source-unit factor divided by the destination-unit factor.
Worked example
For a floor or land surface area of 100 ac converts to 0.4046856422 km².
- Start with 100 ac.
- Multiply 100 by 0.004046856422.
- Report 0.4046856422 km², rounded to the precision of your original measurement.
Check the reverse conversion
1 km² = 247.1053815 ac. Use the square kilometer to acre converter to calculate in the opposite direction. This has its own formula and reference table.
Definitions that matter
One square foot is 0.09290304 square meters. Do not convert square feet using the linear foot-to-meter factor. An acre describes area, not the length or shape of a boundary.
The base unit for this category is m². One ac corresponds to 4,046.856422 sqm; one km² corresponds to 1,000,000 sqm. These definitions explain the relationship rather than relying on a rounded display value.
Sources and precision
Definitions: NIST Guide to the SI. Calculations use double precision; the tool defaults to a readable rounded result, while tables show up to ten significant digits. Displaying more digits does not increase the accuracy of the original measurement.
Read our calculation methodology and content standards, or continue with metric and customary measurement conventions.