Three-dimensional patterns have been widely considered for the generation of lightweight internal structures in design methodologies for additive manufacturing. Accordingly, triply periodic minimal surfaces patterns have been previously explored due to their improved mechanical performance compared to traditional lattice structures. The present study analyses the effect of the design parameters on relative density of Primitive and Gyroid patterns. Results show a linear correlation between the relative density and pattern’s thickness, and a non-linear relationship to length. Relative density equations are proposed to ultimately aid in the pattern’s dimensions selection based on manufacturing constraints for their applicability in topological optimization procedures.