For XL Size, Please Add 1 Full Inch on Either End of Large Measurements Listed.

Small:
Chest: Up to 36″; Waist: 22″-30″; US Women’s Size 0-8; US Child’s size 7-14

Medium:
Chest: 36″-44″; Waist 30″-36″; US Women’s Size 8-12; US Child’s size 14-16

Large:
Chest: 42″-50″; Waist: 36″-42″; US Women’s Size: 12-16

X-Large:
Chest: 48″-56″; Waist: 44″-50″; US Women’s Size: 16-22

Backpacks are one size.