How to measure the dog size?
Chest: measure the thickest part of the chest, add 2~3CM will be better. (Usually behind the two legs)
Length: Make sure your dog stands properly, not sitting or lying. Measure along the dog's backbone from the base of the neck to 5CM front the base of the tail.
Neck: the girth of the neck, add 2~3CM will be better.
Note: If your dog is a large chest, long hair, or at the high end of the size, you may order the next larger size to ensure a comfortable fit.

Size Details:
This dog clothes is for small toy dogs or cat under 20 pounds / 10KG
Size S: Neck: 23cm/9.0inch Back: 20cm/8.0inch Chest: 32cm/12.5inch; for weight 2.7-4.4 pounds/1.25-2.0 KG
Size M: Neck: 26cm/10inch Back: 25cm/9.5inch Chest: 37cm/14.5inch; for weight 4.4-6.6 pounds/2.0-3.0 KG
Size L: Neck: 29cm/11.5inch Back: 30cm/11.5inch Chest: 42cm/16.5inch; for weight 6.6-9.4 pounds/3.0-4.25 KG
Size XL: Neck: 32cm/12.5inch Back: 35cm/13.5inch Chest: 47cm/18.5inch; for weight 9.4-13 pounds/4.25-6.0 KG
Size XXL: Neck: 35cm/13.5inch; Back: 40cm/15.5inch Chest: 52cm/20.5inch; for weight 13-19.5 pounds/6.0-9.0 KG

Breed Recommend: (for reference only):
Size XXS,XS: teacup, kitten,puppy,chihuahua ( weight under 2lbs/1kg)
Size S,M,L: cat,puppy,chihuahua, pomeranian, maltese, yorkshire terrier (weight 3-10lbs/1.5-4.5kg)
Size XL.XXL: toy poodle,papillon,shih tzu,mini doberman,bichon frise,pekingese,jack russell terrier,miniature schnauzer,pug(weight 11-20lbs/5-9kg)
The recommend weight is just for reference, please kindly take a measurement of your dog before buy,thanks.