Paper shredder thickness calibration using a Hall effect torque detector coupled to a paper shredder motor, producing a signal corresponding to the paper shredder motor rotation, a controller receives the signal and determines a paper shredder motor torque from the signal corresponding to the rotation of the paper shredder motor, with the torque corresponding to shreddant thickness. Signal is compared to predetermined maximum signal beyond which overload is signaled.Also, a method of operating a paper shredder having a rotating motor to comminute shreddant, including providing a Hall effect rotor and sensor; creating a torque signal based on a full load motor torque, and comparing the current torque signal to the full load torque signal.