With Bundler

gem 'unite'

Without Bundler

gem install unite

Based on the algorithms developed by Gordon S. Novak, Jr. at the University of Texas, which can be found here:

http://www.cs.utexas.edu/users/novak/units95.html

Handles the following dimensions:

[:length, :time, :temperature, :mass, :current, :substance, :luminosity]

Can use Unite::Quantity to represent values or include the functionality into your own objects.

Look at https://github.com/stellard/unite/blob/master/lib/unite/quantity.rb for a minum implementation

TODO: Needs more info here.

Unite::Quantity.init("1000*km")
Unite::Quantity.init("1000","km")

Unit definitions are found here:

https://github.com/stellard/unite/blob/master/lib/unite/lookup/definitions.rb

Specs show good examples of use.