In July, 2011 Radamradam asked:
Does anyone know how to determine the true size of an iPhone app (including any content the apps may have downloaded within themselves)?
In October, 2011 LostinAsia responded:
Just following up on this a few months later: in iOS 5 this is now possible; go to Settings / General / Usage. After the wheel spins for a bit, you'll see a list of how much memory each app is using. Click on an app to get a breakdown of the "App Size" (what you can see in iTunes, and in the iTunes store) and then the separate "Documents & Data" (other material you've added). So, for example, I figured out that most of my extra memory came from a Chinese dictionary (which I won't mess with), but there were also a lot of scanned PDFs buried deep in an app that I'd totally forgotten about - and I got 1GB of memory back.
This tip generated from the original discussion: Actual App Size (iTunes is incorrect)