A model is developed for calculating NO emissions for stratified charge engines in which the fuel is completely vaporized prior to combustion. The validity of the model is limited to single chamber geometry as it does not treat bulk gas motion typical of prechamber or divided chamber designs. The parameters of the model are fuel type, humidity of inlet air, overall equivalence ratio, stratification function, per cent EGR, intake manifold pressure, intake manifold temperature, compression ratio, piston connecting rod to crank radius ratio, RPM, and position and duration of combustion in the cycle.