Abstract: A device for calibrating cubes which are used in the determination of the magnitude and pressure of an air blast having a base, a pedestal mounted on the base, a pendulum pivotally attached near the top of the pedestal, a box end for holding the cube at the end of the pendulum, a timing device for determining the velocity of the pendulum during its swing, and a bumper for stopping the pendulum when the pendulum is vertical so as to impart an initial velocity of Vo to the cube whereby the calibration factor of the cube can be determined. Another embodiment provides a metallic block instead of the box end in which case the cube is struck by the block end of the pendulum thus imparting initial velocity Vo.