Abstract: The system (SIMAC) presented in this study allows simulation and adjustment of 24 growth models as well as to estimate nutrient requirements for beef cattle. To adjust linear and non-linear models, the LeastSqX (Newcastle Scientific) software was incorporated within a routine in the programming language Microsoft visual basic 6.0. To check the operation of the SIMAC, the Curve expert 1.4 and Number Cruncher Statistical Software (NCSS), 2007 programs were used to adjust the growth models to data from weight records (CDP; AMCC). From the verification and comparison of SIMAC with other systems, results were highly satisfactory, obtaining similar results. The SIMAC differs from other model adjustment systems in a posteriori handling of the estimated results. This system can be used to analyze factors that affect the productive efficiency of cattle growth and carry out an analysis of sensibility of required nutrients for estimated growth.