Chalcopyrites are a material class widely used in thin film solar cell manufacturing, with the most prominent industrially applied example being CIGS (CuInGaSe2). In order to maximize the effectiveness of these solar cells and minimize the cost, the search for appropriate alternative materials is still ongoing. In this work, we show that the lattice parameters of chalcopyrite are linearly dependent on electronegativities and ionic radii of their constituent elements, and the corresponding analytical expression is provided. The results of the research have a wide range of potential applications, including chalcopyrite band gap evaluation and experimental use, for example, for predictions of lattice parameters for heteroepitaxy.