18 or 20 gauge
5.0 mm or 4 Guage
18gauge is about 1.02mm.
For a standard nostril piercing, 18 g.
The standard gauge for most ear piercings, such as earlobes, is typically 20 gauge. However, cartilage piercings may be done at a slightly larger gauge, often 18 or 16 gauge. It's important to consult with a professional piercer to determine the most suitable gauge for your specific piercing.
Either 16ga or 14ga
A little over 1".
Probably 19 gauge, which is 1.067 mm
For wire gauge, 1.25 mm diameter wire is closest to 16 gauge (AWG). See related link.
12 gauge is thicker than 14 gauge.
1 mm = 4/100 inches
.953 mm (USG)