Prestressed concrete is widely used in the design and construction of bridges due to its versatility and cost-effectiveness. The methodology for analysing prestressed structures presents peculiar characteristics, particularly regarding calculations that require evaluating the beam sections individually, considering different limit states. This research focuses on the development of a computational program to support the tendon layout of simply supported prestressed beams used in bridge design. It is based on the premise that there are few free software tools available for structural design, with an even greater shortage in the field of prestressed concrete and bridge design. Therefore, the development of the software Protensor was identified as a necessity. The algorithm implemented in the program was developed in the C# programming language, which is widely used and stable, offering extensive libraries and ease of creating a user-friendly graphical interface that facilitates user interaction. The software is capable of performing the preliminary design of the beam’s cross-section, calculating the envelopes of internal forces, generating prestressing stages, defining the tendon geometry, calculating and iterating prestress losses, and verifying the structural performance under limit states. It discretizes the beams into structural sections, based on the Brazilian design standards NBR 6118 and NBR 7188. The results obtained through the use of Protensor were consistently validated against the available technical literature by applying it to real-world bridge projects with superstructures composed of simply supported prestressed beams.