mm/25.4 = inches. Example 17/25.54 = .669", this is the marking on my 16 gauge Halifax/Darne bores. Nominal 16 gauge size is .662 inch or 25.4 times .662" = 16.8 mm. All you need is a little hand held calculator & remember that number of 25.4 conversion factor.


Miller/TN
I Didn't Say Everything I Said, Yogi Berra