This is the method we use for garments that the manufacturer does not make a size chart for. 

Since we don't have any perfect size 4, 8 and 12 models just lying around, we put the garment on the hanger and measure it across three key areas. 

We recommend that you find a similar garment that fits you well and take the same measurements, then order one that matches or exceeds all three of your garment's measurements.

Size Small: A=18", B=15", C=20"

Size Medium: A=19", B=16", C=21"

Size Large: A=20", B=17", C=22"

Size XL: A=21", B=18", C=23"