Three numbers decide whether a piece fits: gauge, length, and — for rings — diameter. Get them right and everything else is taste.
Gauge is thickness
Gauge measures the thickness of the bar, and it runs backwards: a higher number is thinner. It is the one measurement you cannot change on a whim, because it has to match the hole you already have.
| Gauge | Millimetres | Usually |
|---|---|---|
| 20g | 0.8mm | Lobes, some nostril |
| 18g | 1.0mm | Lobes, lighter cartilage |
| 16g | 1.2mm | Most ear cartilage |
| 14g | 1.6mm | Heavier cartilage, industrial |
If you do not know your gauge, ask whoever pierced you. Guessing and buying too thin leaves the hole loose; too thick will not go through without stretching it.
Length is how thick your ear is, plus room
Post length is measured along the bar between the two ends. It needs to match the thickness of the tissue, with a little clearance — too tight and it presses, too long and it catches.
While healing you want extra room for swelling, which is why a fresh piercing takes a longer post than the same piercing does a year later. A healing helix takes 8mm and settles at 6mm. A forward helix takes 6mm and settles at 5mm.
Diameter is for rings
Inner diameter is measured across the inside of the ring. Most ear placements sit between 6mm and 10mm.
The conch is the exception: a ring there has to clear the entire outer edge of your ear to close, so it runs to 10mm or 12mm. Measuring by eye does not work — ask your piercer.
If you are not sure
Use the fit finder. Tell it the placement and how old the piercing is, and it will give you the gauge and length rather than making you work it out.