The present study is concerned with steady-state slag foaming. First, the various models presented in the literature are briefly reviewed and their accuracy in predicting steady-state foam thickness is evaluated by using a wide range of experimental data. Then, a correlation is developed by applying the Buckingham's Pi theorem to variables commonly used in previous studies on slag foaming. However, the concept of foaminess has been disregarded as it is an idealization that is not supported by experimental evidences. A power type of law has been assumed between the four dimensionless numbers derived. The empirical coefficients are obtained using experimental data reported in the literature. They cover a wide range of operating conditions and foaming fluids with appreciably different chemico-physical properties. The predictions of the correlations compares well with experimental data. The dimensionless numbers derived from the Buckingham's Pi theorem and the associated empirical coefficients are found to be similar to those obtained by performing a dimensional analysis of the governing equation for the transient foam thickness which could not be predicted a priori. Finally, the dependency of the average bubble radius with surface tension is discussed. Overall, the predicted thickness decreases with increasing surface tension thus satisfying basic thermodynamics considerations.