To determine the position of rotationally drivable tools in machine tools, the moment of separation of the tool to be measured and a measuring beam, for example a laser beam of a light barrier, is used. The tool to be measured is first positioned in such a manner that the measuring beam is interrupted, and is then moved to a measuring position in which the moment of separation of the tool and the measuring beam occurs, and the measuring beam is no longer interrupted by the tool during at least one complete revolution. The moment of separation is used to determine the position of the tool.