The UDUNITS package supports units of physical quantities (e.g., meters, seconds). Specifically, it supports conversion between string and binary representations of units, arithmetic manipulation of units, and conversion of numeric values between compatible units. The UDUNIT-2 package differs from the original UDUNITS package in the following ways: support for non-ASCII characters, support for logarithmic units, persistent value converters, improved API, XML unit database, and no Fortran or Perl API.

WWW: https://www.unidata.ucar.edu/software/udunits/
