The master curve methodology proposed by Kim Wallin (ASTM E1921-02) has been used to evaluate master curve reference temperature (T₀) from full compact tension (CT) and 1/2T-CT specimens for the material 20MnMoNi55 steel using single temperature and multi-temperature method. The effect of temperature range, number of test temperatures and initial crack length on the value of T₀ are also studied. The correction proposed for thickness adjustment has been verified. Master curves are drawn using full and 1/2T-CT specimen separately and compared with best fit characteristic curve and found to be within 95% bound.