I am in a medieval re-enactment group. A few times a year someone asks me to make garb for them. I took the measurements of a lady I think of as "large" yesterday. That's it, just large. And discovered much to my surprise that she's 12" larger in the bust, 17" larger in the waist, and 11" larger in the hips than I am! She's 1/2" taller.
Amazing what a difference nice wide shoulders make in how well you can distribute weight and carry off a larger stature.
I been told I'm wrong, but I think of myself as having an "average" build. I'm not little. I'm 5' 8-1/2" and just a tad under optimal BMI. I need to lose about 5 pounds in the right place (stomach) to be my "ideal" which is shapely, but not thin (won't happen - weight loss always shows in the bust first).