A lifting device comprises a support element and an actuator for pivotably moving a lifting arm. A load cell outputs a load signal from the actuator. A first torque sensor outputs a first torque signal from at least one of a pivot between the lifting arm and the support element and along the lifting arm. A second torque sensor outputs a second torque signal from at least one of the pivot between the actuator and the support element, the pivot between the actuator and the lifting arm and along the actuator. A displacement sensor outputs a displacement signal from the actuator, and a calculator calculates a weight at a distal end of the lifting arm based on the distributed load signal, first and second torque signals, and the displacement signal.
