The paper proposes a one-dimensional model for predicting gas entrainment into a non-evaporating full cone steady spray injected into a stagnant gas at uniform pressure. The main outcome is a law relating the entrained mass flow rate to injected mass flow rate, gas properties, mean droplet diameter and axial distance from the nozzle. A comparison with available experimental data is presented. The model allows the apparent inconsistency of the experimental results obtained under different conditions to be eliminated by identifying two new non-dimensional parameters.