To determine if your dog's collar is too tight or loose around their next, you should try the "two finger rule." If you are able to comfortably slide your index and middle fingers between your dog's neck and collar, then it is properly fitted on them. If you can slide in more than those two fingers, the collar is too loose; if you can't slide in those two fingers (or your fingers are squeezed in), then the collar is too tight and should be loosened up a bit.