The research deals with supply air jets in air-conditioned rooms which have different lengths. The study was conducted according to the numerical method using the Fluent software package. Discharge conditions are equal in all cases. As a result, dependences of main kinematic and geometric jet’s characteristics (width and jet range, longitudinal velocity profiles, axial velocity, average velocity of the back flow, flow rates in the cross sections of the direct and back flows, distribution of static pressure along the length of the jet) on longitudinal constraint parameter are determined (length of room). The calculation results are presented in the form of corrections to the characteristics of a free jet, taking into account the influence of longitudinal constraint. It is found that influence of Archimede’s buoyant force on the temperature distribution along the length of non-isothermal jet is inconsequential. Dependence of dimensionless temperature on the jet axis of dimensionless length of the room of the coordinate x̄ is determined. The results can be used in calculation of airflow circulation in different purpose air-conditioned rooms.