L - by Anthropologie Black NEW $178 Button Front Short Sleeve Midi Dress 0416JW

Measurements: 

Because sizes tend to vary among brands, we take approximate measurements with the garment lying flat and unstretched.

For the best fit, take a tape measure and compare a similar garment from your own to  find out what size you are. The following measures are essential: 

Chest (from armpit to armpit): 19.5"

Length (neckline to hem): 49"