Based on the conventional ray‐tracing principle, a fast numerical algorithm is developed that calculates averaged propagation loss and reverberation of underwater sound. The averaging is performed by summing incoherently the contributions of individual ray bundles to each of the rectangular cells into which the range/depth plane is divided. The resulting matrix description of the average intensity field is used to calculate reverberation. The propagation‐loss algorithm is preliminarily tested against mathematical test functions and measured data.Subject Classification: [43]30.20, [43]30.40; [43]85.84.