Dimensional is a library providing data types for performing arithmetic with physical quantities and units. Information about the physical dimensions of the quantities and units is embedded in their types and the validity of operations is verified by the type checker at compile time. The wrapping and unwrapping of numerical values as quantities is done by multiplication and division with units. The library is designed to, as far as is practical, enforce/encourage best practices of unit usage. Version 1 of the dimensional package differs from earlier version in that the dimension tracking is implemented using Closed Type Families and Data Kinds rather than functional dependencies. This enables a number of features, including improved support for unit names and quantities with statically-unknown dimensions. Requires GHC 8.0 or later.