The International Association for the Properties of Water and Steam (IAPWS) develops formulations for the calculation of thermophysical properties of water as a function of different combinations of temperature, density, pressure, enthalpy, and entropy. These properties are useful for scientists and nuclear, chemical, and mechanical engineers who analyse experimental data or are involved with projects and equipment development, like heat exchangers, turbines, or nuclear power reactors. The IAPWS-95 formulation solves the fundamental equation of Helmholtz free energy as a function of temperature and density. This paper gives a description of how these equations are solved and exemplifies the use of a package developed for the free platform R. The IAPWS95 package was developed to help users to get access to the IAPWS-95 formulation in a free software environment which is growing exponentially. Transport properties were programmed using other IAPWS releases. The examples consider the uncertainty analysis of thermal parameters of a nuclear power reactor and the preparation of tables and graphs of water properties.