Resumo. For maximum growth and yield of forest quality, scientific studies are needed on management techniques that will result in a higher economic return. A technique widely used in the production forest is thinning, it increases the individual growth of remaining trees. The aim of this study is to develop a system of curved guides to express the potential number of trees per hectare can maintain the forest as a function of dominant height, as an aid in determining the thinnings. The data were provided by the companies Cambará SA, Klabin SA, Forestry SA and United Petropar, where 187 samples were collected, being two dominant trees for unit, adding up to 374 dominant trees. In the selection equation, it was considered the statistical parameters of the adjusted coefficient of determination (R² adj), coefficient of variation (CV), F value and calculated value of chi-square (χ²) and analysis of waste. The equation selected was number 5, however, we observe that equations 5 and 6 are very similar for all the selection criteria used. Comparative analysis of regression equations developed independently for the three sampling regions showed significant differences between them. As there was no interaction between the variable “place” and the ‘hdom’ variable, a regression was calculated for Site 2 and one for Places 1 and 3 because these regressions differed significantly only on the intercept, with parallelism. The residue analysis showed that the equations developed for each site showed no tendency to over-or underestimation, therefore, the use of dominant height as the independent variable is efficient to describe the guidelines for thinning in Pinus taeda L. studied.