The pattern making process is a key step in the development of apparel products. In this process, it is necessary to develop basic patterns, which serve as basis for the interpretation of different types of clothes.The purpose of this article is to present the automation of the basic patterns design process for women's pants construction. To do so, we used the Grasshopper parametric modeling program, which is a plugin of the Rhinoceros software. This system allows a parameterization of shapes, in a way that allows an adaptation of measurements of the geometry created.For the development of the tracing of the basic models of the women's pants, we used the steps indicated in the garment modeling method proposed by Romero (1995). The process in the Grasshopper uses mathematical operations and tools for drawing points, lines and curves.With the automation of the basic mold tracing, it is possible to adapt parameters according to the measurement chart of individual companies or customers.This adaptation also assists in the creation of several custom patterns, such as other types of pants and shorts, which can be interpreted through the basic pattern of pants. In a comparative analysis with the traditional method, the moldsgenerated in the Grasshopper obtained high fidelity in comparison to the tracing done manually, which allows the development of the molds without loss of quality. In this context, this project also aims to collaborate in the construction of a set of basic patterns that support the development of custom clothing.