Gauge Sizes
There are different types of gauge sizes used for body jewelry. In the US, the system used is American wire gauge or Browne & Sharpe system. The smaller the diameter, the larger the gauge.
Basic Facts and General Information
Body jewelry measurement is conducted using micrometer, Vernier Gauge, calipers or gauge wheel by its outer diameter. Measurement for medical needles is done by measuring the tube’s inner diameter. For example, the 16ga needle has a 14ga diameter. With piercing needles, they are always measured at the outer diameter.
Majority of the body jewelers utilize gauges from 18 and 00ga. The diameter difference between gauges is about 20%. The measured size is used for the bigger gauges.
Body Piercing Gauge Measurements
Different gauges are used for body piercings. But most of them are done between 14ga and 10ga. It will all hinge on the piercing. There are gauges beyond 00ga. But those generally use half inch or imperial sizing. These are general guidelines only; other sizes may be used.
Gauge Sizes and Their Equivalents
18ga is equal to 0.040 in or 1.024 mm. 14ga is equivalent to 0.064 in or 1.628 mm. 12ga is equal to 0.081 in or 2.053 mm. The 10ga size is equivalent to 0.102 in or 2.588 mm.
8ga is 0.128 in or 3.264 mm. 6ga is the same as 0.162 in or 4.115 mm. 4ga is the same as 0.204 in or 5.189 mm. 2ga is the same as 0.258 in or 6.544 mm. 0ga is the same as 0.325 in or 8.251 mm. 
The 00ga size is equal to 0.365 in or 9.266 mm. The 000ga is the same as 0.410 in or 10.41 mm. The 0000ga size is similar to 0.460 in or 11.68 mm. 00000ga is equivalent to 0.517 in or 13.1 mm.
Gauges in Fractional Size
14ga is equivalent to 1/16", while 12ga is the same as 5/64". 10ga is the same as 1/10". 8ga is equal to 1/8". 4ga is the same as 13/64" while the 2ga is 1/4" in factions. 0ga is 5/16" while 0000ga is 15/32". 00000ga is equal to 33/64". Note: it is difficult to give gauges of various household objects became of the different scales used.
If you are unsure of what gauge size to use, consult a body jeweler or someone who specializes in body piercings. It is the quickest and surest way to determine the right specs for you.
