All bicycles use imperial chains, even if the rest of the bike is metric. So chain wear is most easily measured using an imperial scale. Place the edge of a rule along the chain whilst the chain is under normal tension, taking care that it doesn't sag (hang the chain vertically if it is off the bike). Place the zero marker over the top of a link pin, and observe what is happening at the 12" marker (you can use a shorter rule if necessary, but the longer the rule the more accurate will be your measurement). According to Sheldon Brown, if the link pin is less than 1/16" past the mark, all is well, so this year-old chain, at less than 1/32", is healthy. If the link pin is 1/16" past the mark, you should replace the chain, but the sprockets are probably undamaged. http://www.sheldonbrown.com/chains.html
