Acre to Square Kilometer (ac to km²)
Result
0.004046856422 Square Kilometer
Formula
km² = ac × 0.004046856422
1 ac = 0.004046856422 km², and 1 km² = 247.1053815 ac.
Area factors are the square of the length factor: 1 ft = 0.3048 m, so 1 ft² = 0.3048² = 0.09290304 m². The acre is 43,560 ft² (4,046.8564224 m²) and the hectare 10,000 m².
Worked examples
- 1 ac × 0.004046856422 = 0.0040468564 km²
- 10 ac × 0.004046856422 = 0.040468564 km²
- 100 ac × 0.004046856422 = 0.40468564 km²
Common mistakes
- Do not apply a length factor to an area: 100 m² is 1,076.39 ft², not 328 ft² (100 × 3.28).
- A plot described as "20 × 30 ft" is 600 ft²; convert each side to metres first or convert the area afterwards — never just one side.
Acre to Square Kilometer table
| Acre (ac) | Square Kilometer (km²) |
|---|---|
| 1 | 0.0040468564 |
| 2 | 0.0080937128 |
| 5 | 0.020234282 |
| 10 | 0.040468564 |
| 20 | 0.080937128 |
| 50 | 0.20234282 |
| 100 | 0.40468564 |
| 1,000 | 4.0468564 |
The units
- Acre (ac)
- 43,560 square feet, exactly 4,046.8564224 m². 640 acres make a square mile.
- Square Kilometer (km²)
- 1 Square Kilometer = 1,000,000 Square Meter.
Sources for these factors
- Handbook 44 (2024), Appendix C: General Tables of Units of Measurement — NIST
- Guide for the Use of the International System of Units (SP 811), Appendix B: conversion factors — NIST
Last reviewed against these sources. An automated check recomputes every factor from its definition on each build. How we check accuracy