I'm going to be using the term "penis size" here to mean the size of the glans penis when measured from the tip of the foreskin to the head of the penis, or at least when it is exposed.
My biggest penis is 4" long, and my smallest penis is 2". It's important to keep in mind, that in many cultures around the world, the length of the foreskin is not considered a good thing to keep; it is usually discarded and is often tied up in knots and left on the floor of a house to dry out, and then thrown away when the weather becomes warmer. Here is a quick guide on what it looks like: The white area on the back of the penis is a foreskin, and the red area is the glans, and it has to be the size of the glans that's measuring you when it is removed. I think I was about 3", but it's hard to tell for sure. It's hard to see if it's a good thing or not. There are people who think it is, but if they were measuring a child, they would have no idea what size the baby would be.