I use a steel rule, which I'm sure is a lot easier than using a tape measure.
Which measurement tool do you use. Do you have the Park Tools one?
http://www.parktool.com/product/chain-wear-indicator-CC-3-2
I actually have this one
http://www.parktool.com/product/chain-checker-cc-2
but I don't think it particularly matters which one you get. It's just that the difference between a good and worn chain is tiny, so I think it's worth getting one.