Within this master’s thesis, a measurement system was designed and assembled for the calibration of a standard relative humidity meter. Calibration was performed in the Laboratory for Process Measurement at the Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb. The basics of air humidity measurement and the basic terms related to humidity measurement are given. Various methods for calibration of relative humidity meters are explained. The methods used for calibration performed within this master's thesis are calibration using the primary dew-point generator and comparison calibration by measurement of dew-point and temperature of sample air. For both methods, the used equipment and the calibration procedures are described. Before the final presentation of the measurement results, the measurement uncertainty assessment is described, since measurements are incomplete without an assessment of the quality of the results. Along with the calibration uncertainty, all the terms that are relevant to its determination are explained. At the end, the results of the calibration were analyzed and displayed in a table and graphically. For all measurement points, the mean values obtained by the reference device and device under calibration are given, together with corresponding corrections and expanded measurement uncertainties.