Available models of fire risk assessment can still hardly be used for practical engineering problems. They are mostly loosely integrated, complex, computationally demanding applications, and require additional pre- or post-hand-calculations. However, the latest achievements in computer science enable establishing an easy-to-use web-application with access to enormous computing power in a cloud requiring minimal management effort. In this article, we present a new tool for probabilistic fire risk assessment called Aamks. Our goal is to build an easy-to-use, science-based, practical engineering tool to support building design in day-to-day work. To meet the overall goal, we aim at working out an integrated, web-based application with computational efficiency and scalability allowed by cloud computing. Aamks performs a stochastic analysis of life safety in building fires using deterministic models for fire and evacuation and stochastic sampling of the uncertain input parameters.