We report an experimental method to estimate the bias dependence of the perpendicular spin torque in magnetic tunnel junctions. This method utilizes the pulse-width-dependent change in the switching phase diagram and addresses the perpendicular-torque-driven precessional switching at high-bias ranges where the in-plane spin torque acts as an additional damping. The bias dependence of the perpendicular spin torque at high bias was found to be linear for a voltage polarity. This method will be useful to address spin torque effects in magnetic tunnel junctions at high bias.