Units for Ruby

An extension to Ruby's Numeric classes that adds support for units of measure.

Examples

Creating numbers with units

    require 'units'

    three_meters = 3.meters
    two_meters = 2.m
    one_inch = 1.inch

Note that you can't use 1.in because 'in' is a reserved word in Ruby.

You can also make fancier units by passing arguments...

    square_meters = 3.meters(2)

    speed   = 3.meters.second(-1)
    gravity = 9.81.meters.per_second(2)

    future  = 88.miles.per_hour	    # No need for roads
    hertz   = 440.per_second	    # A lovely A4 note

Converting units

    3.meters.inches          # => 118.1103 inch
    10.inches.mm             # => 254.0 millimeter

Checking for units

    three_meters = 3.meters
    three_meters.meters?     # => true
    three_meters.inches?     # => false

Supported Units

All of the SI units listed below allow any of the standard SI prefixes to be prepended to the unit name. Actually, the US Customary units support the SI prefixes too, but that's not a typical usage.

Note that the names listed here are the symbol names used by the Units gem, and are derived from the proper names of the units. They don't exactly match the proper unit names to maintain consistency and to respect Ruby's naming conventions.

SI Primary Units

meter
gram
second
ampere
kelvin
candela
mole

SI Derived Units

hertz
radian
steradian
newton
pascal
joule
watt
coulomb
volt
farad
ohm
siemens
weber
tesla
henry
celsius
lumen
lux
gray
sievert
katal
becquerel

SI Abbreviations

Some combinations of SI units and prefixes are both verbose and commonly used. Enough so that it makes sense to support their abbreviations. The supported abbreviations are listed below.

mm -> millimeter
cm -> centimeter
km -> kilometer

US Customary Units

Head over to the Wikipedia article on US Customary Units to learn about all of these bizare units and their namesakes.

Area

acre
section
township

"International"

point
pica
inch
foot
yard
mile

Mass

grain
dram
ounce
pound
hundredweight
long_hundredweight
short_ton
long_ton
pennyweight
troy_ounce
troy_pound

Nautical

fathom
cable
nautical_mile

Survey

link
survey_foot
rod
chain
furlong
statute_mile
league

Temperature

fahreheight
rankine

Volume

acre_foot
minim
fluid_dram
teaspoon
tablespoon
fluid_ounce
jigger
gill
cup
pint
quart
barell
hogshead

bfoz/units-ruby