In this paper, simple approximate formulas are established to estimate active and reactive power losses in distribution networks. The developed formulas based on load profiles are derived from Elgerd's power loss formulas. A simple model is also proposed to estimate the load profile while considering several parameters, such as the average load demand and the load limitations. Derivation of the load model and the loss formulas are presented along with their applications on two distribution networks. The results show that the loss formulas, which depend on the proposed load profile, can estimate the power losses in distribution networks with high precision.