This String Gauge Converter below has been supplied for your convenience.

Origins of our gauging system 
The gauging system I use has its' origins around the turn of the century when they decided to split the millimeter into 20 equal parts. So each gauge number is equal to a 20th of a millimeter. So for example .90mm equals 18 gauge. The easy math is to divide ( or multiply) by 5 and move the decimal point two places to the left. The system is useful because the gauge numbers also translate easily into English measurments by multiplying by 2 and moving the decimal three places to the left. So 18 gauge would equal .036 inches. 