Printing size?

[OurJud]

I'd like to knock out a few prints for friends and family and am looking for some advice on the size and resolution I need to be working at to give me a a print of 'wall-hangable' size (maybe 8 inches square).

I currently work at 600px square / 300 PPI, but converting px to inches seems to be far more confusing than I imagined.

Any and all advice very welcome.