Different types of measurement There are 3 different ways to measure with calipers. 1.Measuring the external dimension of a part. To do this clamp on the outside using the external measuring jaws. EX: Measuring the side lengths of a cube. 2.Measuring the internal dimension of a part. To do this clamp on the inside using the internal measuring jaws. EX: Measuring the slot width or diameter of a circle in a part to confirm tolerances. 3.Measuring the depth of a part. To do this use the depth gauge at the end of the calipers. EX: Measuring to the bottom of a threaded hole to pick out the right sized bolt.