Cracking due to shrinkage constitutes a common issue for damage to concrete industrial floors, which can have large economic effects. The awareness of how to design slab-on-ground in regards to shrinkage cracking is inadequate and shrinkage cracking is often disregarded in design situations. This study aimed to improve the prediction of how to choose a proper slab dimension regarding the risk of shrinkage cracking. That prediction is based on the finite element method (FEM) analysis and the maximal principal stress in a slab. Besides that, for the slab with a fixed shorter side and the fitted stress function of the slab, we determined the optimal length of the longer side of the slab. The approximation of the stress function is obtained by the linear least squares method based on data sets defined by results from FEM analysis. The established numerical model and results indicate improved possibilities of understanding and modelling the shrinkage behavior of slabs-on-ground.