I have a 8 to 10 pound dachshund mix and the large size fit her perfectly. It was difficult to pick the correct size because she is longer, but I got it right on my second try, and I gave the XL pajama to my 14 pound dog. so glad because they are so cute.
This fabric material shrink in the dryer sadly . The seams are also starting ripping. I have only had it one day. It is still good for the money but I will look for better material next time.