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 Skip Navigation LinksMath Help > Physics > Non-SI Units

Non-SI Units

Click here for SI units like meters, kilograms, and seconds.  SI stands for Syst�me International, which consists of the base units of length, mass, temperature, time, and charge.

Distance (length):

Point: 1/72 inch, as in 12-point type, which is 12/72, or 1/6 inches tall.

Inch: exactly 0.0254 meters

Hand: 4 inches.

Span: 9 inches.

Foot: 12 inches.

Cubit: 18 inches.

Yard: 3 feet.

Smoot: 67 inches.  It's a long story.

Fathom: 6 feet.

Rod: 16.5 feet.

Chain: 66 feet, or 4 rods.

Furlong: 660 feet, or 1/8 mile.

(Statute) Mile: 5280 feet, or 1760 yards.  A mile is exactly 12*5280 inches, which is exactly .0254*12*5280 meters, which is exactly 1609.344 meters.

Nautical Mile: once 6080 feet, now exactly 1852 meters, by international agreement, which is 6 076.11549 feet.

Cable: 1/10 of a nautical mile.

League: 3 Nautical miles.

Light year: approximately 9.4605284 � 1015 meters, the distance light travels in one year.

Parsec: approximately 3.08568025 � 1016 meters, or 3.26163626 light years

Area:

Acre 43,560 square feet, or 1/640 square miles.

Volume:

[U.S.] Fluid Ounce: about 0.0295735297 liters

[U.S.] Pint: 16 fluid ounces, about 0.473176475 liters, or about 4.73176475 � 10-4 cubic meters

Imperial Fluid Ounce: about 0.960760333 US fluid ounces, or about 0.0284130742 liters

Imperial Pint: 20 imperial fluid ounces, about 1.20095042 US pints, 0.568261485 liters, or 5.68261485 � 10-4 cubic meters

Board foot: 144 cubic inches, used to measure and express the amount of wood in trees.

Velocity (speed):

Knot: 1 nautical mile per hour

Internet references

Wikipedia: Units of length is a good place to learn about really obscure units of length, such as the "beard-second".  Even better: Wikipedia's list of unusual units of measurement

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