Abstract Due to the inherent complexity of the cold roll-forming process, machine design procedures have remained highly empirical. There is little information available on the calculation of roll load, though a prior knowledge of this load is essential for the optimum design of the roll stands and the smooth forming of the strip. The present paper describes a semi-empirical method for calculating the roll load. The method is based primarily on equating the external work to the internal dissipation of energy. The estimate has also been modified to take account of the reverse bending of the deformed strip after it reaches the next roll station. The theoretical results have been verified by roll-forming channel sections of mild steel and aluminium and measuring the load with a specially designed quartz dynamometer. The agreement between theory and experiment has been found to be good in spite of the many assumptions which are necessary to simplify the analysis. The results also show how the roll load depends on the material properties, the geometrical parameters of the produced section and the machine dimensions.