chest measurements:

With the garment lying flat, measurement is taken from the armpit seam at the side seam, across the front to the opposite armpit at the side seam. Measurement is in inches.

hem measurements:

With garment lying flat, measurement is taken side seam to side seam, along hemline, front only. Measurement is in inches.

back length measurements:

With the garment lying flat, measurement is taken from the middle back of the neck, falling down to the hem. Measurement is in inches.