<p><strong>Background.</strong> The empty body weight (EBW) represents exactly the animal mass and is used as a base to calculate most of the nutrient requirements in most feeding systems. <strong>Objective.</strong> To evaluate models for estimating EBW in growing hair sheep in a feedlot system under tropical conditions. <strong>Methodology. </strong>One hundred fifteen male growing hair sheep lambs (Pelibuey, Black Belly, and Katahdin) between four to ten months of age with a mean shrunk body weight (SBW) of 34.50 ± 7.40 kg (± SD) were used. The relationship between SBW and EBW was assessed by means of three models: Eq. 1. Linear with intercept; Eq. 2.- Linear without intercept and Eq. 3.- Allometric. The predictive ability of models was evaluated by cross-validation. <strong>Results. </strong>The correlation coefficient among SBW and EBW was high (r = 0.98). The regression equations had high determination coefficients (r²) of 0.97. Based on the evaluations Eq.1 had the performance compared with other models. The following final model was fitted to estimate the EBW as a function of SBW of growing castrated male hair sheep: EBW (kg): -2.39 (± 0.53***) + 0.95(± 0.02***) × SBW (kg). <strong>Implications. </strong>These results contribute to the development of mathematical models for more accurate weight adjustments in growing hair sheep in a feedlot system under tropical conditions<strong>. </strong><strong>Conclusion.</strong> The equation developed and evaluated in the present study revealed that the linear relationship between SBW and EBW can be used to predict EBW in hair sheep, for that the use of this model can be safely applied to male hair sheep. In addition, it was found that the relation BW/EBW was on average 1.18 for males. </p>