Calliper, also known as caliper, is an instrument made for measuring internal or external dimensions. It can be used to measure point to point distances to mark the skin for piercing or for measuring the diameter of circular body jewelry pieces. Calliper is an instrument that piercers often use for various procedures. It typically includes hinged legs that can open and close easily. The other part of the instrument are special slides that use as indicators. The indicators can also be digital, depending on the model. The scale shows the measurement when the legs of the instrument are used to measure distance. The most common application in piercing studios is to measure the distance on the skin so proper spots can be marked for piercing.

Most callipers used for piercing also have inverted legs. These legs are used for measuring body jewelry pieces. It is possible to insert the inverted legs of a caliper into a circular jewelry piece such as a ring or a circular barbell. The calliper can be used to measure the inner diameter of these body jewelry pieces. This diameter is important for measuring the right size of circular jewelry so calliper can be of great help in body jewelry stores or even for individuals who want to know the exact diameters of their body jewelry pieces.