In a method for measuring mechanical workpieces by tomography, a workpiece and radiation penetrating the workpiece are moved relative to one another step-by-step. A two-dimensional image of the workpiece is generated in an imaging plane from the interaction of the workpiece and the radiation in each movement position of the workpiece. In addition, a three-dimensional representation of the workpiece is computed from the two-dimensional images. From at least two two-dimensional images showing a regular actual structure existing within the workpiece, points at a high-contrast transition are registered. A three-dimensional equivalent body is determined from the position of the points, and said equivalent body is compared to a predefined nominal structure.