Phase retrieval is a highly useful technique that allows the calculation of the complex electric field of a beam of spatially coherent radiation based only on recordings of intensity profiles with a camera. In this work, we demonstrate what we believe, to the best of our knowledge, is a new technique for single-beam multiple-intensity phase retrieval based on simultaneous propagations that provides improved fidelity results compared to standard methods (0.9931 compared to 0.9646) and a 34 dB reduction in background noise level. The implementation is fast, open source, user friendly, and can be run on either CPUs or GPUs. It is available for download at https://gitlab.gbar.dtu.dk/biophotonics/PhaseRetrieval.