Predicting the quality of a machined component is the grandiose signification in manufacturing industry. Calculation of the cutting force is one of the most important elements to predict the quality of machined parts. In this paper, a linear force model is developed in which the cutter’s helix angle is incorporated to calculate the cutting force coefficients for the milling process. On the effect of cutter’s helix angle, all derivations of cutting forces are directly based on the tangential, radial, and axial cutting force components. In the developed mathematical model, with the stable milling condition, the average cutting forces are expressed as a linear function of the feedrate, and the cutting force coefficient model is formulated by a function of average cutting force and cutter geometry such as cutter diameter, number of flutes, cutter’s helix angle. An experimental method is proposed based on the stable milling condition to estimate the cutting force coefficients. This method can be applied to each pair of cutter and workpiece. The developed cutting force calculation model has been successfully verified by both simulation and experiment with very promising results. Integrated application with a virtual three-axis milling machining simulation system has also been implemented to demonstrate potential utilization of this developed model.