A novel method is proposed for predicting the combined global damage index through newly developed formulae utilizing recorded floor-displacement data, local and global capacity-based parameters for 3D RC buildings. Multilinear regression analysis is performed to develop the new formulae for predicting the global damage index obtained from modified Park and Ang-type 3D local damage indices. Further, explicit expressions for the global damage coefficients of the new formulae are developed as a function of structural properties and soil type for wider applicability of the formulae. The computed global damage indices are found to represent the damage states of RC buildings satisfactorily.