In 2023, the European Association of National Metrology Institutes (EURAMET) launched project 22RPT01 TracInd BVK-H. Project's main objective is to improve the traceability and reliability of hardness measurements using optical measurement methods, namely Brinell, Vickers, and Knoop (BVK) tests. One of the outcomes of this initiative is to assess how hardness measurements can be affected by possible influencing variables. Within this framework, this thesis tries to determine the sensitivity coefficients and related uncertainties for BVK methods that link hardness to the temperature at which the test is performed. The temperature range (15-35°C) used is that permitted in ISO standards for end users, such as a company's testing laboratory.