In the world of body jewelry, the gauge system can be a bit counterintuitive. The lower the number, the bigger the gauge. So: 16 gauge is bigger than 18 gauge. This can be confusing because the gauge system for body jewelry is counterintuitive. The lower the number, the thicker the jewelry. So: 16 gauge is approximately 1.2mm in diameter 18 gauge is approximately 1.0mm in diameter This means 16 gauge jewelry is about 0.2mm thicker than 18 gauge jewelry. While this difference might seem small, it's significant in the world of body piercings.