How much tissue can be healed?

Now this question is pretty general and I’m not wounded :) I’m hoping for something like a formula even though this would contain a lot of variables (like location and size of the wound, how much blood is reaching the wound etc.).

What I was actually wondering is under which circumstances a seriously injured finger would still heal. Worst case scenario being badly skinned since I already know a finger won’t heal without bone. Not even sure for whom I added that.