This repo is the home of the units package for Haskell, which provides a mechanism for compile-time dimensional analysis. There are two components of this project, units and units-defs. The units package implements all the type-level machinery for dimensional analysis, but it is completely agnostic to the actual system of units used. Separately, the units-defs package (which depends on units) defines commonly used units, including implementing the SI (Système Internationale) system of units.
Look at the README for units for more info.