Hi Dave. My 2c worth from playing about:
I'd firstly print off at the measured size if a tight fit is needed. The filament always shrinks a bit when printing, so you're likely to end up with 9.something mm for a 10mm measurement.
If it ends up under/oversize I just guess, judging it by eye and getting closer and closer.
For example, I've just made some bushes for the riving knife on my table saw. I needed a tight fit and ended up going a mm oversize for the bush in the design, then filing it down ever so slightly to be able to tap it in snugly to the hole.
Sorry for not offering a more scientific explanantion. I'm sure others will have one!