Interactive piercing gauge chart: 16g=1.2mm, 18g=1.0mm, 20g=0.8mm, 12g=2.0mm. Expert sizing by Patrick Poli, BioFlex® creator.
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"As a piercer, I hated seeing 'near enough' jewelry sizes. A fraction of a millimeter is the difference between a comfortable heal and a migration disaster. I built this converter to be the clinical bridge between confusing gauge numbers and the exact millimeter precision I demand in my own manufacturing."
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</iframe>The gauge system in body piercing comes from the American Wire Gauge (AWG) standard, a historical system where higher numbers mean thinner wire. So a 20g needle (0.8mm) is very fine, while an 8g barbell (3.2mm) is quite heavy. This counter-intuitive scale confuses clients and apprentices alike, which is why professional piercers and manufacturers use millimeters as the precise standard.
When a piercing is performed, the fistula (the channel) is created at a specific diameter. A fractional mismatch between the needle and the replacement jewelry can cause excessive trauma or "cheese-cutter" migration, where the jewelry slowly cuts through tissue. Matching your replacement jewelry to the exact millimeter of your healed track is a clinical requirement, not a preference.
Earlobe piercings are typically performed at 20g (0.8mm) or 18g (1.0mm). Navel, nipple, and tongue piercings are usually 14g (1.6mm). Septum piercings are commonly 16g (1.2mm) or 14g (1.6mm).
For stretched lobes, the jump from 2g (6.0mm) to 0g (8.0mm) is a full 2mm, requiring careful, staged stretching over time to avoid tears or blowouts.
It comes down to history and inertia. The gauge system was borrowed from 19th-century electrical wire standards and simply stuck. It is a logarithmic scale, so each step is roughly a 12 percent change in diameter, which is genuinely useful when you are planning a stretch.
The catch is that it reads backwards to anyone new: a 14g barbell is thicker than a 16g, not thinner.
After three decades of this nomenclature being baked into the trade, it is not going away. My own rule is to always state the millimeter equivalent next to the gauge, for example "16g / 1.2 mm", so nobody is ever guessing about what they are actually ordering.
See body jewellery at real size on your screen, and try it on before buying.
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