Hotskillet, You will enjoy your new tool on many projects, not just checking your chain elongation. If you do another search on this site try using ' elongation' with ' chain'.....
These days it is very easy to get answers by just trying a Google.com search....
For instance , I just typed in " inches to metric convert" and got this list... take your choice...
http://www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=inches+to+metric+convert&btnG=Google+Search