i've been told it's easier to gauge the rat's size by the size of the fattest part of the snakes body and so far it's been good going here. i dont do well with a bunch of numbers anyways, especially percentages...
i go trying to figure all that out.
when i buy my feeder rats i just tell the guys to give me the smallest of their smalls and & when i feed 'em to my girl they leave a small but still noticeable bulge in my girl's belly.