Diffusers are widely used in technical practice in order to make the transition from a tube/pipe or duct of smaller section to a larger one. Low pressure drop across a diffuser is highly required to save pumping or ventilation work. Diffuser pressure drop is caused by enhanced turbulence of the flow, separation of the boundary layer from the diffuser walls and violent vortex formation. As a result, the precise pressure drop coefficient estimation is of high importance. The pressure drop coefficient (?d) of a diffuser depends on diffuser geometry and flow parameters. Traditionally, a number of models must be combined and used with the data obtained from tables (with 2-D interpolation) and charts in a series of steps to obtain ?d. This approach is not suitable for computer-based simulations. Consequently, in this study, a semi-empirical model, for estimating ?d of a conical diffuser, as an explicit function of the flow parameters and the diffuser geometry, is developed. The model was validated using literature data. The performance indices which were obtained as high R2=0.9942, low mean absolute relative error (MeARE)=4.04%, low root mean squared error (RMSE)=0.0192 are an indication that the proposed model is accurate enough for computer-based simulations and performance evaluation of a conical diffuser over a wide range of operating conditions.