Most definitely not! I wish I could see into the future, but just like with children you can't predict adult height/weight. The best I can do is provide the heights and weights of the parents. The dogs in my program range from 10" - 14" in height and weigh 6-20 pounds.  We have had pups that range from 5 lbs all the way up to 35 lbs!  Size at birth does not matter. Pups can be fast or slow growers. I have found once the pup is about 3-4 months old you can chart their adult weight at www.puppychart.com. Just choose the breed "Miniature Australian Shepherd and follow the directions. I have found this to be pretty accurate but still no guarantees! Fun fact:  Aussie sizes are based on height, not weight.  Adults 14" and under are considered to be Toy sized, regardless of their adult weight.  A dog that measures above 14" in height is a Mini.  You can learn how to measure a dog's height HERE.