It's really too early to tell. Runts (strictly speaking runts are puppies with a multitude of physical problems at birth)--the smallest puppies at birth may simply be small because the were from a later breeding the the rest of the litter or because of an egg fertilized later than others. Many so called runts grow to sizes that are the same as other litter mates and sometimes the biggest puppies at birth don't end up being the biggest at maturity.
I generally assume that the puppy I've gotten will turn out to be a normal size based on the parents size.
On top of the preceeding information--one of my males was the largest puppy in the litter at birth. When he was in the 6-9 puppy dog classes at shows he was mid range in the sizes. In the 9-12 classes he was the smallest. But he didn't didn't stop growing and in the 12-18 classes he was right in the middle of the size range again.
On the other hand one of my puppies as 28" in the 6-9 classes by the time he was an adult he was 28-1/2"--good thing that there were four other puppies that were equally big when young so he didn't look like a complete misfit.
If you know what sizes the sire and dam were you can maybe make some guesses at adult size but it's easier to just wait and see how tall they are by the time they are 15 to 18 months old.
dobebug
