Belly button rings are the jewelry inserted into a navel when it is pierced. Most initial navel piercings are done with a curved barbell, a piece of jewelry consisting of a stainless steel bar with beads that unscrew at both ends. Less commonly, captive bead rings may be used. A captive bead ring, or CBR, is shaped like a C, with a bead held in place by pressure between the two ends. Rings are measured by gauge and diameter, while barbells are measured by gauge and length.

Wash your hands and piercing with antibacterial soap and warm water. Dry well and remove the jewelry from the piercing.

Unscrew the beads from the ends of the bar if your jewelry is a curved barbell. Leave the bead out if your jewelry is a CBR.

Use a ruler or dial calipers to measure the distance across the ring. Measure across the inside; do not include the ring itself in the measurement.

Determine if the bar of your barbell is internally or externally threaded. External threading means the ends of the bar look like screws; internal threading means the ends are hollow. If the jewelry is externally threaded, use a ruler or dial calipers to measure the bar itself, between the threads. If the jewelry is internally threaded, measure the entire bar.

Use a wire gauge wheel or dial calipers to measure the gauge of the jewelry. If using a gauge wheel, slip the bar into the 14-gauge hole first. If it doesn't fit, try the 12- or 16-gauge holes.