I have a 10lbs shihtzu . I bought a medium size (thinking it would be best to get the next size ) and it was still too small .My pup looks pretty darn cute and always gets compliments! Definitely Runs small so size up. My only complaint would be that I wish there was an opening on the back for a harness. I did ended up cutting out a hole and it works but otherwise it’s so cute!I love this for spooky season and also keeps kitty warm, since it does a bit chilly in our house and she loves to crawl under a blanket. This hoodie is super cozy she doesn’t mind putting it on and it also doesn’t restrict her from doing her cat tasks such as jumping and a little bit of mischief here and there :)14 lb grumpy cat skeleton says he hates this costume. I don’t care what he hates. Humans polled all say he wears this costume very well despite not wanting to snap it closed on his tubby floofy tummy. I like the snap closure, makes it easier to dress a cat who would otherwise prefer to remain naked for Halloween.We have a white Malteses and this looked really cute on him!Fits the puppies perfectly. This will help keep them warm for a cold Halloween this year.Super cute !!!!Fit great definitely recommendPerfect for Halloween camping kept our Sophie warm and still in costume.