Non-SI Units

Click here for SI units like meters, kilograms, and seconds.  SI stands for Système 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 strange units of measurement.

Related pages on this website

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The webmaster and author of the Math Help site is Graeme McRae.
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