Abstract: A measuring device for determining the longitudinal dimensions of elongated and/or planar objects, such as boards and planks or plates, the device comprising a horizontal measuring platform (1) comprising at least at one predetermined point a stopper (2) against which one side or end of the object to be measured is positioned, the measuring platform (1) being supported by means of weighing sensors (4a, 4b, 5) from below at least at two points (4, 5) which are positioned at a predetermined distance from each other and at predetermined distances from said stopper (2), whereby the weighing sensors are connected to an electronical calculation unit to which output signals from the weighing sensors (4a, 4b, 5) are applied and which calculates the length of the object on the basis of the ratio of the output signals from the weighing sensors.