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U.S. Survey Foot: Revised Unit Conversion Factors
Approximate decimal SI equivalents for measures commonly given in U.S. survey feet and exact equivalents for the foot that will be adopted beginning January 1, 2023 and published in NIST Handbook 44 (Appendix C, General Tables of Units of Measurements) and will be published in NIST Special Publication 811, The NIST Guide for the use of the International System of Units.
|
Units based on the foot |
Unit type |
Exact U.S. customary definitions based on the foot, plus other exact definitions |
International foot metric equivalent (exact) |
U.S. survey foot |
|---|---|---|---|---|
|
foot (ft) |
length |
Defined with respect to meter |
0.3048 m |
0.304 800 609 601 m |
|
cable’s length |
length |
720 ft = 120 fathoms |
219.456 m |
219.456 438 913 m |
|
chain (ch) |
length |
66 ft = 4 rd = 100 li |
20.1168 m |
20.116 840 234 m |
|
fathom |
length |
6 ft |
1.8288 m |
1.828 803 658 m |
|
furlong (fur) |
length |
660 ft = 10 ch = 40 rd |
201.168 m |
201.168 402 337 m |
|
league |
length |
15,840 ft = 3 mi |
4828.032 m |
4828.041 656 083 m |
|
link (li) |
length |
0.66 ft = 0.01 ch |
0.201 168 m |
0.201 168 402 m |
|
mile (mi)(a) |
length |
5280 ft = 8 fur = 80 ch = 320 rd |
1609.344 m |
1609.347 218 694 m |
|
rod (rd), pole, perch |
length |
16.5 ft = 0.25 ch |
5.0292 m |
5.029 210 058 m |
| square rod (rd2), square perch, square pole | area | 272.25 ft2 = 0.0625 ch2 | 25.292 852 64 m | 25.292 953 812 m |
|
acre (ac) |
area |
43,560 ft2 = 10 ch2 = 160 rd2 |
4046.856 422 4 m2 |
4046.872 609 874 m2 |
|
square mile (mi2) |
area |
27,878,400 ft2 = 640 ac |
2 589 988.110 336 m2 |
2 589 998.470 319 521 m2 |
|
acre-foot |
volume |
43,560 ft3 |
1233.481 837 547 52 m3 |
1233.489 238 468 149 m3 |
(a) Also referred to as the “statute mile.” Although historically defined using the U.S. survey foot, the statute mile can be defined using either definition of the foot, as is the case for all other units listed in this table. However, use of definitions based on the U.S. survey foot should be avoided after December 31, 2022 except for historic and legacy applications.