I was hesitant about the 'one size' sizing, but too cheap to spring for the next size up. I'm a size 12 or 14P in GAP and Loft clothing and the waist on this was okay after a large dinner. Not loose enough so I don't notice it at all, but not tight enough that it's uncomfortable. However, it is tighter than my regular waistbands. This is not surprising since my 34 lb 4 y.o. tried it on and the skirt did not fall right off. In other words, I believe this can be worn by the size 00 out there.

Also, mine (purple) is ridiculously pouffy. (Perfectly fine for an 80s costume party.) It puffs out on me more than it does on the model in the picture.