A method calculates a calibration parameter for a robot tool. The method is based on the reception of an image dataset from medical imaging of an image volume via a first interface. The image volume contains a part of the robot tool and the robot tool is attached to a robot. A robot dataset is received by a second interface. The robot dataset contains a position of a movable axis of the robot during the recording of the image dataset. The position and/or orientation of a marking in the image dataset are determined by a computing unit. An image-based position and/or orientation of the tool center point of the robot tool are calculated by transforming the position and/or orientation of the marking. The calibration parameter is calculated based on the robot dataset and on the image-based position and/or orientation of the tool center point via the computing unit.
