The listing, Olivia Moon Top has ended.
I got this top off of Listia but unfortunately it doesn't fit me. I'm thinking it's a Large but here are the measurements :
Armpit to armpit about 20.5"
Adjustable tie for waistline/slightly below waistline, measures from dream to seam about 20-21" not tied.
From the button to the bottom of top is also 21"
Back from top to bottom is 27"
I hope this helps so you can enjoy wearing this top because it is so cute!