All measurements in inches. 

These are the dimensions are when the garment is laying flat (before stretch). 

PENELOPE TANK
SIZE CHART XS S M L XL
LENGTH 18 5/8 19 5/8 20 5/8 21 5/8 22 5/8
ACROSS SHOULDER 10 3/8 11 1/8 11 7/8 12 5/8 13 3/8
CHEST 12 1/8 13 1/8 14 1/8 15 1/8 16 1/8
ARMHOLE DEPTH 6 3/4 7 1/4 7 3/4 8 1/4 8 3/4
BOTTOM OPENING 13 1/2 14 1/2 15 1/2 16 1/2 17 1/2