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# U.S. Survey Foot: Revised Unit Conversion Factors

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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
metric equivalent (approximate)

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

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.

Created September 23, 2019, Updated January 4, 2023