General Tables of Equivalents–Units of Length, Area and Volume

In these tables it is necessary to differentiate between the “international foot” and the “survey foot.” Therefore, 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 millilitre.

Units of Length
angstrom (D) = 0.1 nanometer (exactly), 0.000 1 micrometer (exactly) ,0.000 000 1 millimeter (exactly) ,0.000 000 004 inch
1 cable’s length = 120 fathoms (exactly) , 720 feet (exactly) , 219 meters
1 centimeter (cm) = 0.393 7 inch
The angstrom is basically defined as 10-10 meter.

Units of Length
 1 chain (ch) (Gunter’s or surveyors) = 66 feet (exactly), 20.116 8 meters
1 decimeter (dm) = 3.937 inches
1 dekameter (dam) = 32.808 feet
1 fathom = 6 feet (exactly), 1.828 8 meters
1 foot (ft) = 0.304 8 meter (exactly)
1 furlong (fur) = 10 chains (surveyors) (exactly), 660 feet (exactly), 1/8 U.S. statute mile (exactly), 201.168 meters
[1 hand] = 4 inches
1 inch (in) = 2.54 centimeters (exactly)
1 kilometer (km) = 0.621 mile
1 league (land) = 3 U.S. statute miles (exactly), 4.828 kilometers
1 link (li) (Gunter’s or surveyors) = 0.66 foot (exactly), 0.201 168 meter
1 meter (m) = 39.37 inches, 1.094 yards
1 micrometer = 0.001 millimeter (exactly), 0.000 039 37 inch
1 mil = 0.001 inch (exactly), 0.025 4 millimeter (exactly)
1 mile (mi) (U.S. statute) = 5280 feet survey (exactly), 1.609 kilometers
1 mile (mi) (international) = 5280 feet international (exactly)
1 mile (mi) (international nautical) = 1.852 kilometers (exactly), 1.151 survey miles
1 millimeter (mm) = 0.039 37 inch, 0.001 meter (exactly)
1 nanometer (nm) = 0.000 000 039 37 inch
1 Point (typography) = 0.013 837 inch (exactly), 1/72 inch (approximately), 0.351 millimeter

Read Also :
● General Tables of Units of Measurement
● United States Units of Measurement Table
● British Units of Measurement
● List of all Units of Measurement 

The term “statute mile” originated with Queen Elizabeth I who changed the definition of the mile from the Roman mile of 5000 feet to the statute mile of 5280 feet. The international mile and the U.S. statute mile differ by about 3 millimetres although both are defined as being equal to 5280 feet. The international mile is based on the international foot (0.3048 meters) whereas the U.S. statute mile is based on the survey foot (1200/3937 meter).

The international nautical mile of 1852 meters (6076.115 49 feet) was adopted effective July 1, 1954, for use in the United States. The value formerly used in the United States was 6080.20 feet = 1 nautical (geographical or sea) mile.

Units of Length
1 rod (rd), pole, or perch = 16½ feet (exactly), 5.029 2 meters
1 yard (yd) = 0.914 4 meter (exactly)

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 acres
[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 acres, 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

Units of Capacity or Volume
1 barrel (bbl), liquid = 31 to 42 gallons¹⁴
1 barrel (bbl), standard for fruits, = 7056 cubic inches
vegetables, and other dry = 105 dry quarts
commodities, except cranberries = 3.281 bushels, struck measure
1 barrel (bbl), standard, cranberry = 5826 cubic inches, 8645/64 dry quarts, 2.709 bushels, struck measure
1 bushel (bu) (U.S.) struck measure = 2150.42 cubic inches (exactly)