Stress indices and the appropriate simplified design formulas are developed for analyzing piping reducers according to the philosophy of Section III of the ASME Boiler and Pressure Vessel Code for Class 1 piping systems.Relatively simple equations based on extensive analytical parameter studies and related experimental data from the literature are developed for the evaluation of primary-plus-secondary and peak stresses due to internal-pressure and bending-moment loads.These simple formulas may be used directly by designers and/or incorporated into the codes and standards.Indices for primary stresses are discussed, but additional information is needed before definitive recommendations can be made.