A simple quantitative measurement procedure of in-plane cantilever torsion for calibrating lateral piezoresponse force microscopy is presented. This technique enables one to determine the corresponding lateral inverse optical lever sensitivity (LIOLS) of the cantilever on the given sample. Piezoelectric coefficient, d(31) of BaTiO(3) single crystal (-81.62 +/- 40.22 pm/V) which was calculated using the estimated LIOLS was in good agreement with the reported value in literature. c 2011 American Institute of Physics. [doi: 10.1063/1.3660806]