Particle number emission rate is one of the important parameters that characterizes the emission source and it is an essential input to the aerosol dynamics models. Estimation of this quantity at the source is rather complicated due to the combined action of ventilation and coagulation on the depletion of particle number concentrations. Techniques to estimate number emission rate are still at preliminary stage and hence there is a definite need to develop a methodology for this purpose. In the present study, an effective coagulation coefficient (Keff) approach is provided to correct for coagulation losses encountered during experiments for the determination of number emission rate. Keff is expressed as a function of single parameter (β) namely the ratio of the prescribed ventilation rate and measured number concentration in the experiments. The utility of the approach is demonstrated by applying it to few practical cases reported in the literature. The results are further discussed.