This project describes the redesign of a free software, which can be executed in any operating system, for the calculation of thermal loads in air conditioning and refrigeration systems using the CLTD/CLF method proposed by the American Society of Refrigeration, Heating and Air Conditioning Engineers (ASHRAE). The development of the software was accomplished in three stages: updating and expansion of the environmental and technical information required, development of the software in which the MVC (Model-View-Controller) development method was used and JAVA as programming language and real case tests to verify the functionality of the software. The software needs as minimum system requirements JAVA 7 or higher, 128MB of RAM, disk space of 124MB and Intel Pentium 2 or higher processor and Windows 7 or higher for Windows, iOS X 10.7.3 or higher on Mac and Linux operating packages compatible with the required JAVA version.