Bust is measured from underarm seam to underarm seam across the front. Double to get the circumference.  The length is measured from the shoulder seam to the hem in the center and the hem on the side.  The Kendal Green does run smaller 
Kendal Green: 
Medium: Bust is 19.5" (39" around), center length is 24.5", side length is 29"
X-Large: Bust is 21.5" (43" around), center length is 26", side length is 30"
1x: Bust is 22" (44" around), center length is 26.5", side length is 32"
2X: Bust is 23" (46" around), center length is 27", side length is 32"