A piezoelectric stack actuator (PSA) consisting of 28 lead magnesium niobate-lead titanate (PMN-PT) piezoelectric single crystal layers is developed. The free stroke and blocking force, which are the figures of merit of a PSA, are simulated through finite element analysis. The free stroke of the PSA samples measured using a laser displacement sensor was in the range of 6.4–8.0 µm at 200 V. In addition, the blocking force of the PSA samples measured using a custom-made system, consisting of a strain gauge, a motor and a load cell, was in the range of 191–226 N at 200 V. An analysis of seven samples exhibited that a large free stroke resulted in a blocking force of the PSA. • The piezoelectric stack actuator consisting of 28 PMN-PT piezoelectric single crystal layers is designed and fabricated. • The systematic experimental setup to reliably measure the blocking force of the piezoelectric stack actuator is described. • The free stroke and blocking force of the piezoelectric stack actuators are characterized.