The estimation of energy content of municipal solid waste (MSW) is normally done by the use of modified Dulong equation (MDE). The MDE requires changing all MSW components to percentages of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sulfur (S), which is very time-intensive effort. An easier-to-use and more practical new equation is presented, which directly uses the percentages of MSW components. The validity of the new equation is checked against MDE by utilizing MSW component data for 35 countries and 86 international cities. A linear regression coefficient (R2) of 0.97 between energy content values (Btu/lb) for the new equation and MDE indicates an excellent closeness. The new equation energy values are about 1–10% higher than the MDE values. The energy content of developing and underdeveloped countries is a half to one-third of those for the developed and highly industrialized countries. About 50–70% of the energy content of MSW is due to the paper component. The new equation offers a goo...