Device for coupling a trailer

The invention relates to a device, which can be mounted on the rear end of a motor vehicle body, for coupling a trailer or a load carrier unit, comprising a holding arm, which at a first end is fixedly connected to the motor vehicle body during operation and which, at a second end, is configured to support a coupling element, wherein the holding arm is provided with a sensor arrangement with at least three deformation sensors, and wherein the at least three deformation sensors deliver sensor values, on the basis of which at least one force component is determined by means of an evaluation unit.