Bar Length : All gauges have 8-9mm bar length (just the bar, not the base), except 12G with has 2 lengths available.
Base Width : 2mm piece has a 5mm base width. 3mm piece has a 6.5mm base width. 4mm piece has an 8mm base width. 5mm piece has an 8.5mm base width. 6mm piece has a 10mm base width. 8mm piece has a 13mm base width. 10mm piece has a 15mm base width. 12mm piece has an 19mm base width.
Base Thickness : The base on all gauges is about 2mm thick.
GAUGE = Standard measurements for bar thickness.
0.8mm = 20G = Standard size for thin nose bars and rings.
1mm = 18G = Standard size for nose bars and rings.
1.2mm = 16G = Standard size for cartilage bars and rings. septum jewellery, daith, eyebrow and rook jewellery.
1.6mm = 14G = Standard size for belly bars, nipple bars and rings, tongue bars
2mm = 12G
3.2mm = 8G
4mm = 6G
5mm = 4G
6mm = 2G
7mm = 1G
8mm = 0G
10mm = 00G
12mm = 1/2"
14mm = 9/16"
16mm = 5/8"
19mm = 3/4"
22mm = 7/8"
25mm = 1"
Length measurements provided on listings are the distance between ends or sides and does not include the ends or the ring sides.
The images below show where to measure gauge and length on common jewellery styles.