Abstract: A method for three dimensional measurement of objects being conveyed through or moved relative to a measurement frame for, by incremental measurements of height, width and length of the object to calculate cubical and circumscribed volume of the object. Each transmitter/receiver element pair of the measurement frame is calibrated by controlling the amount of the light emitted from the transmitter and the threshold level of the receiver, such that the signal/noise ratio of the receiver lies above a specific limit, simultaneously with the illumination time being kept the shortest possible. By incremental measurements at least one pair consisting of transmitter element and directly opposite receiver element in the measurement frame is activated at time, and an external signal being a function of the movement of the object relative to the measurement frame is compared with the registered signals from the receiver elements for calculation of the volumes.