One of the significance parameters for ensuring the traceability of hardness measurement results is the estimation and calculation of measurement uncertainty due to influence quantities on the measurement itself. Frequently, a definition of influence quantities represents a problem, especially the quantitative determination of its influence on the measurement result. The basic goal of this dissertation was to determine the influence factors on the measurement uncertainty of hardness calibration machines and to establish a model to estimate and calculate the quantitative values of those influences. Two primary areas have been elaborated in the theoretical part of the dissertation: measurement uncertainty and hardness. The meaning of measurement uncertainty and the basic statistical foundation for its estimation and calculation are presented in the part on measurement uncertainty. Hardness is analyzed through historical development and physical significance. This section examines especially the today's agreed model for estimation and calculation of measurement uncertainty, which has arisen from the important research of individual global and national laboratories. In the experimental part of the dissertation, the research has been carried out regarding the influences of individual quantities influences on the measurement uncertainty of the Vickers hardness calibration machine 5030TKV. The basis was the separation of the hardness tester load realization system and the system for measuring the quantity of the indentation in order to analyze the individual influence factors with the goal of reducing their measurement uncertainty. The research and analysis of individual influences on the load of the hardness tester was carried out and the new model for estimation and calculation of the measurement uncertainty was applied. Two different measuring devices with calculated and estimated measurement uncertainties were applied as the systems for indentation analysis. The model for estimation and calculation of uncertainties on the basis of research results was also modified. In the end, interlaboratory comparison measurements were carried out by two European laboratories, one of which is the holder of national and primary standard, and the other one is the holder of the reference Vickers calibration machine. On the basis of this research and its analysis certain conclusions have been adopted which will help the laboratories that have reference and primary Vickers hardness calibration machines in estimation and calculation of measurement uncertainties. Moreover, new models which are applied in the dissertation for uncertainties determination will probably be subject of research in other laboratories and perhaps have significance in modification of models for the estimation and calculation of measurement uncertainty of Vickers hardness.