The most common gauge for septum piercings is 16 gauge (approx. 1.2mm thick), however, your piercer may decide to use a different gauge depending on your individual anatomy. While 16G is the typical starter gauge, some people choose to size down to 18 gauge (approx. 1.0mm thick) or size up to 14 gauge (approx.
Also know, what’s the smallest septum size?
Generally 14g / 16g. 18g is the smallest size that you can use once your septum is healed, I heard that anything smaller than 18g can cause the “cheese cutter” effect.