I am 6' and it is about 8" to my navel- Lying down or standing. Sitting like this guy its not that far.
I don't think the guy is small, but probably not as big as some are saying.
So while I am a little disappointed in the female responses ( I am around 8x5, but I feel like this guy's size.), I understand them.
I think he's around 5.5 x 4.5, which would make him very AVERAGE, but on the smaller end of the average range and small for anyone who really has a size preference for length or girth.
The guy who posted this looks bigger or at least in better shape IMHO.
ETA: I just measured and it is 9" to my navel standing or lying down ( My 8" doesn't qualify as big to the "must reach belly button" size queens I guess), but only around 6.5" sitting the way this guy is. If I sit all the way up it is closer to 5.5". In this guy's situation he may be "close" to his navel, but he isn't. There is another thing to consider, though. If I sit in that position my penis is shorter as it's pushed down and the pubic fat area is pushed up. My best guess is the guy is "average." He might be around 6 inches, but not far from it.