I had to measure this differently as its not only open but crosses the body and as such is so very flexible size wise. It’s probably one size fits most but here are some numbers to give you an idea…
Shoulder to shoulder: About 27″
I measured straight across the back from armhole to armhole, this is NOT doubled, just straight across: 24.5″
Waist–again straight across the back and not doubled: 25″
Hip: free
Shoulder to bottom hem: 25″