A device for determining an optimal size of an intervertebral implant, comprising movable posterior and anterior rods, each rod operatively connected to a pair of posterior and anterior distracting members, respectively. Each pair is movable in opposing radial directions in response to longitudinal rotation of the posterior and anterior rods, and has marks corresponding to the distance the distracting members have moved for the purpose of measuring posterior and anterior disc height. A position indicator allows measurement of longitudinal distance between the longitudinally movable posterior and anterior rods. The device further comprises load sensor plates movable in response to movement of the distracting members, first and second handles pivotally connected to the load sensor plates, a protractor disposed relative to the handles, allowing measurement of an angle between the first and second handles, and a transducer for measuring force applied during distraction.