The clothing is measured flat.  The bust is measured from underarm seam to the underarm seam across the front ( double to get the circumference).  The length is measured from the top of the spaghetti strap straight down to the hem.
This camisole does run true to size. Please call us at 979-249-5757 if you have any questions about sizing.  
Small: Bust is 18.5" (37" around). Length is ~28"
Medium/ Large: Bust is 19" (38" around).  length is ~28"
X-Large : Bust is 20" " (40" around). Length is ~29.5"