### Quick Answer

A vernier caliper can measure external and internal dimensions, and many measure depth as well. Vernier calipers have a fixed scale and a moving scale in two units: Imperial (inches) and millimeters. Typically the bottom half provides external measurements using a fixed point and a moving second point. Internal dimension points are located on the top half, and the sliding portion often includes a rod for depth measurement. Along the sliding portion are additional scales to help measure fraction or decimals to an accuracy of within 1/128 inch or 0.05 mm.

Know More### Full Answer

**Determine which units to use**Imperial units are located on the top half of a vernier caliper, and millimeters on the bottom half. Decide which units you are needing to use.

**Determine what type of measurement to take**For external dimensions, use the points, or jaws, on the lower half and place the object between the jaws. For internal dimensions, use the upper set of jaws, and place the caliper inside the area to be measured, sliding until the jaws cannot move. For depth measurement, use the rod and slide the caliper down until it no longer moves.

**Read the vernier scales**For Imperial units, locate the zero on the sliding scale, and read off units left to right up to the zero. From the zero, read right until one of the tick marks aligns with the tick marks on the fixed scale. The number of tick marks past zero provides the measurement of fractional inches. For metric units, follow the same steps until you get the number of tick marks past zero; this provides the measurement in millimeters up to 0.05mm.