Our dogs Ellie 65lbs wears an XL, Maximus 77lbs wears an XXL

 

Size Chart:
Small Back Length: 10" Chest: 16" (Most Important) Neck: 12"  Weight:  5-10 (approx.)

Medium Back Length: 12" Chest: 20" (Most Important) Neck: 14"  Weight: 10-15 (approx.)

Large Back Length: 16" Chest: 22" (Most Important) Neck: 18"  Weight: 15-25 (approx.)

X-Large Back Length: 22" Chest: 27" (Most Important) Neck: 22"  Weight: 25-40 (approx.)

XX-Large Back Length: 27" Chest: 36" (Most Important) Neck: 27"  Weight: 40-60 (approx.)

3X-Large Back Length: 33" Chest: 40" (Most Important) Neck: 28"  Weight: 60-80 (approx.)