The paper presents the disclosure of the problem of calculating the friction factor. This problem exists in the calculations of head losses for a given flow discharge and the geometric parameters of the pipes. The analysis of the formulas recommended by known scientists is described. The article also presents the shortcomings of the formulas and the variance of the adequacy of the experimental data. These research data were obtained by J. Nikuradze for smooth pipes. We obtained a formula based on the method of dimensional analysis. This formula characterizes the inner surface of the pipes. Also, this formula describes the change in the friction factor from the Reynolds number. The accuracy of calculating the obtained formula is higher than the accuracy of existing formulas.