The aim of this study is to determine an optimum voxel size in the Kahang Cu porphyry deposit (Central Iran) using statistical parameters and vector analysis based on the 26 drilled boreholes. The mean, median and Median Absolute Deviation (MAD) were calculated for total distances between 14 pairs of closest boreholes in terms of X and Y directions. Based on the results, three block models were determined with 3 x 3 x 10 m3, 4 x 4 x 10 m3 and 5 x 5 x 10 m3 of voxel volumes for Cu distribution utilising inverse distance weighted (IDW) method. According to calculation of Non-Zero voxel numbers and decreasing of standard deviations and Cu average values, the block model with 4 x 4 x 10 m3 voxel sizes determined as an optimum block model.