To determine the size of your border collie black lab mix, you'll need to consider these factors:
* Parents' sizes: A mix's size is often influenced by the size of its parents. If both parents are on the larger end of their breed's size range, the puppy is likely to be bigger.
* Gender: Generally, male dogs are larger than female dogs.
* Nutrition: A puppy's diet can influence its final size. A well-nourished puppy will likely grow to be larger than a puppy that is not properly fed.
* Genetics: Some dogs are genetically predisposed to be larger or smaller than others, regardless of the other factors.
It's difficult to predict the exact size of a mixed breed puppy, but you can get a general idea by asking your veterinarian or a knowledgeable breeder. They can give you a better estimate based on the parents' sizes and the puppy's current growth rate.