The 13" inch, I measured (really! with a tape measure - just before posting that comment). And as I said, I based my assumption on myself and how I always use my iPad and when I used a friend's Galaxy tab a while back; We actually talked about it and how you hold it closer than my iPad. Not a lot, bu by an inch or two. So, that's how I "came up" with 11.5" and tailored the resolutions to give me a number close to it... :)