The present paper is dedicated to the practical design of steel hollow sections. It presents a new design philosophy allowing for a direct prediction of the cross-sectional resistance, whatever the loading, yield stress, manufacturing process, cross-section shape and slenderness. In particular, the proposed approach is shown to be able to deal with plastic, compact or slender sections through the same simple and straightforward format. As a consequence, the use of the Effective Width Method for slender sections – which are expected to be met more often in practice with the increasing use of high strength steels is no more needed. In a first step, the paper summarizes the results of an extensive experimental series that helped validating shell FE models. Then, the results of more than 40 000 GMNIA numerical simulations are presented, aiming at characterizing the onset of local buckling with respect to many parameters, such as cross-section shape (square and rectangular tubes), hot-rolled and coldformed fabrication processes, different types of loading situations (from simple load cases to combined ones), different steel grades and various cross-section dimensions and thicknesses so as to cover “plastic” to “slender” responses of the sections. These results are later used to assess the merits of the proposed design approach, and excellent performance is demonstrated, both in terms of accuracy and consistency, which is remarkable given the formal simplicity format of the proposed approach.