A Lab/golden mix will probably be a large dog, somewhere maybe around 25-30 inches at the whithers and 65-85 lbs., but by far not the largest of dogs.
Its called a Labradoodle
They're small when first born because they share their mother's womb with a litter of puppies. So probably on average a few inches, but they grow rapidly.
MALES: 22-24 inches (56-61cm) height 60-80 pounds (27-36kg) weight FEMALES: 20-22 inches (51-56cm) height 50-70 pounds (20-32kg) weight