This package provides support for units of physical quantities. Its main components are: 1) A C library, "libudunits2", for: a) Obtaining a binary unit from a string unit; b) Manipulating binary units arithmetically; and c) Obtaining a converter of numeric values between compatible binary units; 2) A utility, "udunits2", for a) Obtaining the definition of a unit; and b) Converting a numeric value between compatible units; and 3) An extensive database of units.