If people varied as much as our canine buddies, we would range from 2 to 30 feet tall. Dogs' sizes range from 2-pound Chihuahuas to 200-pound mastiffs. Your little buddy stops growing before he's 1 year old, while your gentle giant won't reach full growth until he's 3.
Whether your playful new pal is a small or large breed, he will grow in two significant phases. The first, from birth to 4 or 5 months of age, is rapid as the main part of your puppy's skeleton develops. The second phase is slower. Muscles develop, and your youngster continues to gain weight until he has reached full growth. The duration of this second phase varies considerably, depending on the ultimate size of the adult dog. Because growth in phase one is so rapid, your puppy's energy requirements are double those of an adult dog. He will gobble his food before bouncing off into his daily discoveries.
Large and Giant Dogs
If your loyal pal is a large or giant breed, the first growth phase peaks between 4 and 5 months. During this phase, a large or giant breed can gain 5 to 7 ounces a day. If your gangly friend is a Great Dane puppy, he'll reach half of his adult weight around 5 months, and he'll probably begin to look like he could eventually grow into those huge feet and joints after all. Since growth slows in the second growth phase, most large-breed pups will reach full growth around 15 months. Your Great Dane puppy will continue to grow until he is 2 to 3 years old. If that sweet big pup you brought home is a mastiff, you'll go on wondering if he's ever going to stop growing until he's 3 to 4 years old.
While a large-breed puppy multiplies his birth weight 100 times in his first year of life, your cuddly small-breed pup will multiply his birth weight 20 times. According to The Journal of Nutrition, adult body weight is reached when growth rates fall to zero. A pooch that will weigh 20 pounds or less as an adult reaches his mature body weight between 9 and 12 months of age.
Your puppy grows socially as well as physically. Regardless of breed, social development is relatively the same. From birth to 2 weeks, your newborn buddy's eyes and ears are closed, and he is completely dependent on his mom. At 2 to 4 weeks, he becomes aware of his litter mates. From 4 to 12 weeks, he starts exploring, learns to play, and learns his position within the litter. At 4 to 6 months, your young pal tests where he fits in the structure of the group. At six to 12 months, he's in the adolescent stage. He's rambunctious, inquisitive and continues to develop social skills. He reaches social maturity between 1 and 2 years old. It is then that he will finally understand his rank in your family.
Pauline Gill is a retired teacher with more than 25 years of experience teaching English to high school students. She holds a bachelor's degree in language arts and a Master of Education degree. Gill is also an award-winning fiction author.