A vernier caliper is a precision instrument equipped with two sets of jaws, one for making internal measurements, the other for making extermal measurements. These jaws should be closed lightly on the object being measured. Some vernier calipers also have a depth gauge section. This is a probe, attached to the movable head, which slides along the center of the body and is thin enough to be inserted in deep grroves that may be inaccessible to other measuring devices. A depth gauge section is particularly useful in automotive applications for tasks such as checking the drive train end-float in a final drive assembly (when it is used in conjunction with an engineer's straightedge).

A vernier caliper usually includes both imperial and metric scales and is accurate to about one thousandth of an inch, or 0.02 millimeters.

This tool should be handled carefully and stored in a clean, dry place.

An even more precise instrument used for similar purposes is the micrometer.