A comparative analysis of the experimental values of the hydraulic resistance coefficient λ in the mixed friction turbulent mode zone (ZMF) with the values calculated by the most common calculation dependencies has been carried out. It is found that if the co-equivalent roughness is determined on the basis of the solution of the inverse problem, then any of these formulas can be used to calculate λ in the ZMF with an error acceptable for engineering calculations. To reduce the error of friction head hτ calculation using Leibenzon's formula, the approximation of Altshul's formula was performed, as a result of which new coefficients β and m for ZMF were calculated and the boundary Reynolds numbers for this zone were specified.
