XSmall:

• around the chest measured 7 inches behind front legs (red color on the picture):
  16-20 inches (41-52 cm)
• minimum dog length: 12 inches (30 cm) from base of neck to base of tail.

Small:

• around the chest measured 7 inches behind front legs (red color on the picture):
  24-33 inches(60-84 cm)
• minimum dog length: 16 inches (41 cm) from base of neck to base of tail.

Medium:

• around the chest measured 7 inches behind front legs (red color on the picture):
  23-32 inches(58-81 cm)
• minimum dog length: 21 inches (54 cm) from base of neck to base of tail.

Large:

• around the chest measured 7 inches behind front legs (red color on the picture):
  27-37 inches(69-95 cm)
• minimum dog length: 26 inches (63 cm) from base of neck to base of tail.

XLarge:

• around the chest measured 7 inches behind front legs (red color on the picture):
  36-47 inches (90-120 cm)
• minimum dog length: 28 inches (71 cm) from base of neck to base of tail.