Originally Posted by
DiabloScott
Back in the olden days
, the thumb rule was to lift the chain off the front of the chainring and if you could see the tips of the teeth it was time to re-chain.
That is probably the easiest way.
I did buy one of those digital chain calipers. It is a bit of a pain because it must be calibrated for every use, I think. But, technically it is accurate if one's calibration chain is good.