With the advancement of sensor technologies such as charge coupled devic) and omplementary metal oxide semiconductor, as well as imaging techniques, digital image correlation (DIC) has become a valuable method for deformation measurement in practical applications. In this paper, a MATLAB program based on image correlation coefficient for 2D displacement measurement using DIC was developed, and the reliability of displacement measurement was evaluated based on experimental conditions and program variables. It was observed that when the gray level distribution differs between two specimens, resulting in large gray level deviations in the images captured by DIC, and when the distribution patterns are irregular, the measurement accuracy can be improved. It was observed from the results of rigid rotation tests on specimens with arbitrary patterns that if the subset size in DIC measurement is too small, errors exceeding the range of displacement occur, and if it is too large, errors increase. Based on the measurement results presented in this paper, the appropriate correlation subset size when the magnification factor of the captured images is approximately 10 times was found to be 31, which can be suggested as a guideline for DIC measurements.