One of the most used material model for impact analysis and material fracture simulating is theElastic Plastic with Kinematic Hardening Model, being strain rate dependent plasticity for isotropicmaterials.This material model uses the constants and which are strain rate parameters, known as Cowper-Symonds (from 1983 and Jones) coefficients. Determination of these coefficients is very difficult becausespecial machines are necessary. On the other hand, the technical literature is very poor as these coefficientsare concerned.This paper presents a methodology for determination of C and P coefficients if an experimental curveexists.