The manual conversion of geometrical models for Monte Carlo particle-transport codes is a long and difficult task, especially for complex models of large facilities. This paper presents an automatic tool that converts MCNP geometries to TRIPOLI-4®. We describe the implementation of the converter, we details its limitations and we present a few examples of converted MCNP geometries. We also compare the performance of TRIPOLI-4® on the converted geometries with the performance of MCNP on the original ones.