Payton Piper is brought to offer sizing for ALL shapes, sizes and body types. We order our clothing from many unique vendors which is why we offer measurements in the descriptions of most of our items. For most accurate fit refer to your measurements. 
As a general starting point, please refer to this chart-
                                               SMALL               4-6
                                               MEDIUM              8-10
                                               LARGE                12-14
                                               XL                     16-18
                                               2XL                   20-22
                                               3XL                   24-26