>>3840341Dong calculator. I have the pic, but I've come to feel it's a bit mean, and possibly inaccurate. Reluctant to post it.
To make up for it, I can say Shinji averages at about 4cm flaccid in the manga, going specifically by chapters 50 and 51 where he's nude: but we can see he's submerged or standing in water in all those panels, so he's probably just cold.
There's also no reliable way to determine erect penis size from a flaccid measurement.