Units of Area
| Unit | Divisions | SI Equivalent |
|---|---|---|
| Exact relationships shown in boldface | ||
| 1 square survey foot (sq ft or ft2) | 144 square inches | 0.09290341 m2 |
| 1 square chain (sq ch) or (ch2) | 4356 feet2 (survey) or 16 sq rods | 404.6873 m2 |
| 1 acre | 43560 sq ft (survey) or 10 sq ch | 4046.873 m2 |
| 1 section | 640 acres or 1 sq mi (survey) | 2.589998 km2 |
| 1 survey township (twp) | 36 sections or 4 sq leagues | 93.23993 km2 |
The most widely used area unit with a name unrelated to any length unit is the acre. The National Institute of Standards and Technology contends that customary area units are defined in terms of the square survey foot, not the square international foot. Conversion factors are based on Astin (July 27, 1968) and National Institute of Standards and Technology (2008).
Read more about this topic: United States Customary Units
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