One of the main difficulties in the use of an economic design of reliable optimum values for the design parameters compared with a control chart is the computation of the design parameters n (sample size), h (sampling interval) and k (control limit factor). A very simple procedure is described in this research to determine the design parameters of an x̄ control chart in Duncan’s economic model, such that they minimise the expected total costs per time unit. Numerical examples give more accurate and more published results.