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Optimal design of cold-formed steel (CFS) cross-sections can significantly increase their ultimate load carrying capacity leading to a more economical and efficient structural system. This paper reports on the result of an investigation on optimisation of CFS channel beams subjected to their bending capacity. The optimisation was aimed at maximize strength complying with the manufacturing and constructional restraints. As a result, the selected prototypes and optimisation process met the requirements suggested in Eurocode 3 (EC3). In total, ten CFS channel cross-sections including one novel channel section with the folded flange were considered in the optimisation process. The cross-sectional properties and flexural strength of the sections were determined based on the effective width method suggested in EC3, while the optimisation process was performed using particle swarm optimisation method. The flexural strength of the optimised sections were also obtained using the nonlinear finite element (FE) analysis and the results were compared with those of effective width method suggested in EC3. For the newly-developed folded-flange section, it was observed that the suggested model can predict the bending capacity with reliable accuracy. In addition, compared to their commonly-used standard counterpart and other optimised cross-sections with the same material, this new prototype possesses the highest bending capacity. The bending capacity can also be significantly enhanced by adding edge stiffeners while the effect of incorporating the intermediate stiffeners is negligible and even negative in some cases.