The Units of Measurements module provides a low-level framework for managing units and executing value conversions between different units. This module does not provide much of useful end-user functionality. You are most likely to install it as a dependency for another module. Different units may require different conversion logic. For example, converting KG to LB is just multuplication. However, converting Celsius to Fahrenheit requires a more complicated formula. This module allows you to provide your custom conversion logic via CTools plugins.