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Unit introduces computational units to Ruby. It offers built-in support for binary, mathematical, SI, imperial, scientific and temporal units, and a simple interface for adding your own, custom units.

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  • Define units for operands to avoid the inevitable mistakes that plague unit-less operations.
  • Perform complex mathematical operations while respecting the units of each operand.
  • Get meaningful errors when units aren't compatible.
  • Convert values between different systems of units with ease.


General Usage

require 'unit'
puts 1.meter.in_kilometer
puts 1.MeV.in_joule
puts 10.KiB / 1.second
puts 10.KiB_per_second
puts Unit('1 m/s^2')


Unit(1, 'km') + Unit(500, 'm') == Unit(1.5, 'km')
Unit(1, 'kg') - Unit(500, 'g') == Unit(0.5, 'kg')
Unit(100, 'miles/hour') * Unit(0.5, 'hours') == Unit('50 mi')
Unit(5.5, 'feet') / 2 == Unit(2.75, 'feet')
Unit(2, 'm') ** 2 == Unit(4, 'm^2')


Unit(1, 'mile').in('km') == Unit(1.609344,  'km')
(Unit(10, 'A') * Unit(0.1, 'volt')).in('watts') == Unit(1, 'watt')

See the test cases for many more examples.


Daniel Mendler and Chris Cashwell