In these tables it is necessary to differentiate between the "international foot" and the "survey foot;" the survey foot is underlined. When the name of a unit is enclosed in brackets (thus, [1 hand] . . . ), this indicates (1) that the unit is not in general current use in the United States, or (2) that the unit is believed to be based on "custom and usage" rather than on formal authoritative definition. Equivalents involving decimals are, in most instances, rounded off to the third decimal place except where they are exact, in which cases these exact equivalents are so designated. The equivalents of the imprecise units "tablespoon" and "teaspoon" are rounded to the nearest milliliter.
UNITS OF AREA
| 1 acre |
43 560 square feet (exactly). |
|
0.405 hectare. |
|
|
| 1 are |
119.599 square yards. |
|
0.025 acre. |
|
|
| 1 hectare |
2.471 acre. |
|
|
| [1 square (building)] |
100 square feet. |
|
|
| 1 square centimeter (cm2) |
0.155 square inch. |
|
|
| 1 square decimeter (dm2) |
15.500 square inches. |
|
|
| 1 square foot (ft2) |
929.030 square centimeters. |
|
|
| 1 square inch (in2) |
6.451 6 square centimeters (exactly). |
|
|
| 1 square kilometer (km2) |
247.104 acre. |
|
0.386 square mile. |
|
|
| 1 square meter (m2) |
1.196 square yards. |
|
10.764 square feet. |
|
|
| 1 square mile (mi2) |
258.999 hectares. |
|
|
| 1 square millimeter (mm2) |
0.002 square inch. |
|
|
| 1 square rod (rd2), sq pole, or sq perch |
25.293 square meters. |
|
|
| 1 square yard (yd2) |
0.836 square meter. | NIST Handbook 44, Tables of Units of Measurement |
