This method describes a procedure for measuring the bursting strength of paperboard, including linerboard, employing a disk-shaped, molded diaphragm type instrument. A specimen of board is clamped between two platens with circular openings in their centers. An expansible diaphragm is distended through the lower platen by means of hydraulic pressure until the specimen bursts. The maximum hydraulic pressure when the specimen ruptures is recorded. For the bursting strength of paper, see T 403 “Bursting Strength of Paper”; for that of corrugated and solid fiberboard, see T 810 “Bursting Strength of Corrugated and Solid Fiberboard.”