Originally Posted by gauvins

I have a reasonably good caliper, certified at 0.02mm accuracy.

The problem wrt measuring a bike chain is that the way you position your caliper will have a definite impact on the reading. I took 30+ readings over a couple of weeks, on a slightly used but clean chain. The measurement MAPE (mean average percent error) turned out to be 0.28%. (compare it to the critical value of 0.5% at which a chain might/should be retired and you may conclude that it is too high or somewhat ok). My personal conclusion is that using a caliper isn't particularly useful.

I find it much easier to nail a new chain to the wall use it as a reference for the chains I use in rotation -- I hang the used chain on top of the reference (i.e. hung to the same nail) and retire it it gets close to one link longer. A chain is much cheaper than an accurate caliper, more accurate (probably < 0.05%), and is fast and foolproof.