This paper analyses the perforation depth of metallic plates under cylindrical metallic projectiles impacts. The projectiles are supposed to arrive perpendicularly on the targets. A simplified mechanical model is developed. Its results are compared to the observed values in the case of two series of experiments collected from existing bibliography. An error model is also adopted. A log-normal distribution is adopted in order to take into account the mechanical simplifications as well as the uncertainties that affect the whole governing parameters (projectiles velocity and dimensions, ultimate strength and stress of the target constitutive material, etc). (c) 2006 Elsevier Ltd. All rights reserved.