Elegant Costume Gown

Has a cowl neck, split in back, says one size, but for tall slim to me, here are measurements of a polyester spandex type material. 36in around neck opening, arm openings are 20in around, back of neck to floor 56in, bust is 44in, straight cut to floor equals 44in all the way down.These measurements seem to match 16 so I will put it in plus size. New never worn. I wanted it for toga, but I am short and round.