I have only measured once and that was a while ago.
I asked my Dr. about condoms and he asked me if I knew the size of my penis erect? I said I had not ever measured it. He told me to measure it and he could tell me what size condoms to get.
I used a wooden ruler(on the top side of my penis) and when erect, I placed the ruler up against my pubic bone and to the end of my head, it was just over 9". If I pushed the ruler a little against my pubic area, it was 9 1/4".My penis is straight as a arrow. It doesn't curve.
I used a cloth measure and measured about one inch below the head and I was 7" around. I also measured at the base of my penis and it was about 7 1/8" around. It is the same thickness on the shaft. The head is just a little larger around than the shaft and about 2" long. I am uncut and this was with the skin pulled back off of the glans.
I know there are guys larger and smaller than me but it doesn't matter to me. From what I have heard from guys, it is better to be more average sized than too big. I think I would like to be a little smaller but, that isn't possible. I just have to do with what I have and be proud of it...