Can you tell me how far back should you be able to pull your foreskin?

Here are some ...: May I know why you want to pull far back your foreskin, out of curiosity or for physical/mental comfort? Aside from either, the extent of skin stretchability may highly vary depending upon the duration and degree of asserting stretch. But, how far can it go? I don't believe there has been any study to address the issue in your question. So, ask Doc timely before "self-humiliation".