Abstract: There is disclosed a calliper, useful for measuring how much fat can be pinched beneath the skin, having jaws (4,6) pivotally mounted for relative pivotal movement. The movement is amplified by a gear train (24, 26, 28, and 30). The final gear wheel (30) drives a toothed wheel the movement of which is sensed by an opto sensor (34). A digital readout indicates the spacing between the jaws for indicating the spacing between measuring surfaces of the jaws. In contrast to conventional callipers, which are used only to transfer a dimension from an object to be measured to a measuring device, the callipers disclosed give a direct reading of the spacing between the measuring surfaces.