I recently bought a 19" monitor which I have just discovered (perhaps a little later than I should have...) measures 15"x12". And that's just the screen, not the whole kit and keboodle.
I realise that this may well qualify for daft question of the month, so I'd be eternally grateful if you could keep the mockery at the gentle-mildly scornful level, but is there some measuring system I'm missing out on, or have I been done...?