From the top of the armhole seam to the edge of the cuff.

The measurement is taken just below the underarm, across the garment from side seam to side seam. This measurement is doubled for the bust circumference.

TWaist - At the top of the garment, measured across from side seam to side seam. This measurement should be doubled for the waist circumference.

Hip - From the widest hip point of the garment. This measurement should be doubled for the hip circumference.