A system for the calculation of the weight of a load that is manipulated with the aid of lifting equipment in which there are components a crane arm that comprises a first end with which it is intended that the crane arm is to be mounted such that it can rotate on a crane-support unit, for example a wheeled vehicle chassis that can be driven, and a second end with an end part fixed attached to it which, through a jointed connector that includes an axle bearing, allows the load to rotate around a defined axis of rotation (B, C) relative to the crane arm, whereby the system includes: - a detection means (212A, 212B) that detecting the weight of the load that is being manipulated by the crane arm is integrated into a load-sensitive guide pin (35, 35') that forms part of the axle bearing that is a component of the jointed connection and which guide pin can output a signal that is proportional to the effect that is caused by the load, - a power source to provide driving power for the load-sensitive guide pin (35, 35'), - a sensor cable for the transfer of a driving voltage from the power source to the load-sensitive guide pin (35, 35') in order to drive the same, - a calculation unit that is in signal-transfer connection with the load-sensitive guide pin (35, 35') and that is arranged to calculate the weight of the load that corresponds to the signal from the load-sensitive guide pin, characterised in that the system comprises - an "open joint" that acts as a jointed connector, the axle bearing of which is defined by two joints located at a distance from each other along the joint axle line of the axis of rotation (B, C), where each joint comprises a guide pin (35, 35') of which at least one guide pin in the axle bearing is of load-sensitive type, whereby the sensor cable for the supply of power to the load-sensitive guide pin extends in a compartment that is limited in the direction of the axis of rotation (B, C) between the two joints. - a detection means (212A, 212B) that detecting the weight of the load that is being manipulated by the crane arm is integrated into a load-sensitive guide pin (35, 35') that forms part of the axle bearing that is a component of the jointed connection and which guide pin can output a signal that is proportional to the effect that is caused by the load, - a power source to provide driving power for the load-sensitive guide pin (35, 35'), - a sensor cable for the transfer of a driving voltage from the power source to the load-sensitive guide pin (35, 35') in order to drive the same, - a calculation unit that is in signal-transfer connection with the load-sensitive guide pin (35, 35') and that is arranged to calculate the weight of the load that corresponds to the signal from the load-sensitive guide pin, characterised in that the system comprises - an "open joint" that acts as a jointed connector, the axle bearing of which is defined by two joints located at a distance from each other along the joint axle line of the axis of rotation (B, C), where each joint comprises a guide pin (35, 35') of which at least one guide pin in the axle bearing is of load-sensitive type, whereby the sensor cable for the supply of power to the load-sensitive guide pin extends in a compartment that is limited in the direction of the axis of rotation (B, C) between the two joints.