Abstract: A caliper for the direct reading of the size of nuts, boltheads and fittings. On each leg of the caliper is a linear scale, one scale being calibrated in metric units, and the other in English units. When the terminal tips of the caliper are brought into contact with parallel faces of a fitting, the size of the fitting is read on either scale at the point where the inner edges of the legs intersect. All points on the legs of the caliper translate along concentric arcs of circles which have a common virtual pivot point in space, remote from the upper end of the caliper.