Large to Giant breeds - Birth - 5 months The earlier, rapid growth usually starts to slow down considerably once your puppy reaches 65% of his adult height. Studies done in the UK indicate that you can expect a small or medium breed puppy to reach 99% of it's adult weight somewhere between 9 and 10 months of age. Average growth rates of Giant Schnauzers. Giant Schnauzer Growth Rate Height: * Weight: * *Based on the average growth rates of our own Giant Schnauzers Growth of Giant Schnauzer female: According to its size, the weight of the Giant Schnauzer female at 3 months should be between 9.7 and 12.7 kg. At 6 months, the Giant Schnauzer female weighs on average between 18 kg for the smallest individuals and 23.7 kg for the largest individuals.