All sizing charts are actually measured by Bohemian Inspire.
Item is placed on a flat surface and measured from the shoulder seams or top of strap on a dress with spaghetti straps. All measurements are done on the front of the garment and then doubled.
All sizes are give or take a couple of cm's.
For the best fit, find an item of clothing you already have of similar detail and lay it flat and measure to see if sizes are similar.
DO NOT measure your body as this will not be accurate.
See video on how to measure