Different methods and tools are used to measure concentrations of various gaseous components in engine exhaust gas stream. The concentration usually is measured in parts per million or percent by volume. To compare results between different engines, automobiles or fuels, normalized parameters are more useful. Specific emissions are the pollutant mass flow per distance travelled or unit of power, such as g·km-1and g·kWh-1. There is a lack of description of practically applicable methodology for calculation of specific emissions, particularly, if the FTIR analyser is used. The methodology, presented in this paper, requires measurement of ambient air pressure and humidity, fuel mass flow, engine power or driving speed and concentration of wet or dry exhaust gas components. The methodology includes calculation of absolute air humidity, exhaust gas mass flow and specific emissions.