We present an algorithm that computes the number and the pose (position and orientation) of iceballs in a cryoablation procedure, in order to completely cover the target region, i.e. the tumor. Constraints to needle insertion, such as regions that have to be avoided, are taken into account and satisfied. We developed a tool for cryosurgery planning in MATLAB and perform several simulations to extract information on the algorithm behavior and to verify that it always brings to a complete coverage.