A lot of times recipes (including some of mine) call for dough to be left until it has risen to double the size. I don't know about you but I often end up pottering about whilst my dough rises, then when I go back to check on it's progress i've forgotten what size it was to begin with and can't judge if it's properly proved.

A simple way to figure out the progress of your rise is to take a photo of the dough right after you've plopped it in the pan so you can check it against the proving dough!