Use this "inches to millimeter converter" to find your answer.
Bass Strings are listed in percentages of an inch.
for example 40 gauge is actually .040" or 4 hundreths of an inch. 100 guage is actually .100" or 10 hundreths or 1 tenth of an inch. Get the idea?
So go to this website and plug in your string size using a decimal point as above and it'll convert it to mm or millimeters for you.
http://www.metric-conversions.org/le...illimeters.htm
or you can also use this chart if it suits you better"
http://mdmetric.com/tech/cvtcht.htm
Have fun!

