Last Updated: 27/05/2026
When is a Puppy Fully Grown? Your Guide to Growth Milestones by Breed Size
Ever wonder when your tiny ball of fluff will reach its full size? Our guide covers puppy growth milestones for all breed sizes, the importance of growth plate closure, and how to use nutrition and safe exercise to ensure a healthy adult life.
Author: Dr Maree Monaghan BVSc (Hons)
Reading Time: 8 minutes - short read
One of the most common questions new pet parents ask is when their puppy will be fully grown - and the honest answer is, it depends on size. Most puppies reach full physical maturity between 12 and 24 months of age, with small breeds finishing around 8 to 12 months and giant breeds taking up to two years. Behavioural maturity often takes even longer.
Knowing when do puppies stop growing matters for more than just buying the right-sized bed. It tells you when to switch from puppy food to adult food, when it's safe to step up exercise, and when to expect the last of the growing pains and zoomies. This guide walks through the full puppy growth timeline by breed size, how growth plates work, when to make the food switch, and how to set your puppy up for a healthy adult life.
When is a puppy fully grown? A quick answer by breed size
Adult size is largely determined by breed, and breed size determines how long growth takes:
Toy & Small Breeds (<10kg)
8 to 12 months
Medium breeds (10-25kg)
12 to 15 months
Large breeds (25-40kg)
15 to 18 months
Giant breeds (>45kg)
18 to 24 months
These are guides, not guarantees. Individual puppies vary, and you can confirm by tracking their weight monthly - once it plateaus for a few weeks in a row, your puppy is likely at or near their adult size.
Behavioural maturity lags behind physical maturity. Many dogs don't settle into their full adult personality until 18 to 36 months, particularly larger breeds. So if your one-year-old still acts like a teenager, that's normal.
When do puppies stop growing? The five stages of development
There are generally considered to be five main stages of development in a dog's early life:
The neonatal and transitional stages (birth to 4 weeks)
- Puppies are fully reliant on their mother for food and warmth in their first two weeks, then begin to walk, open their eyes and ears, and start eating solid food.
- Most puppies stay with their mum during this period, so it happens before you meet them.
The Socialisation Stage (4-12 weeks)
- Puppies are weaned from their mother and separated from their litter mates
- They meet new people and animals and settle into a new home
- This is a vital stage for shaping puppies' future behaviour through positive reinforcement training and socialisation
- Careful attention needs to be paid to puppies' nutritional needs to ensure correct bone and muscle growth and healthy development of the digestive tract, nervous system and skin and coat
The Juvenile Stage (3-6 months)
- Growth of small breed pups slows down: it is important to adjust their food intake to ensure they do not become overweight
- Large breeds will continue to grow more steadily and still need approximately double the nutritional requirements of an adult dog of the same breed
- Focusing on establishing routines and setting boundaries is of prime importance for juvenile pups.
Read through our guides to How to Train a Puppy and Addressing Puppy Behaviour Problems for more information.
The Adolescent Stage (6-18 months)
- Smaller breed puppies have usually finished growing
- Large puppies will continue to experience skeletal and muscular growth until they reach their adult bodyweight between 18 and 24 months of age
- Just like human teenagers, adolescent puppies will start to test the boundaries
- They require patience, consistency and engaging activities to help manage their boundless energy. Our guide to adolescent dog behaviour and how to manage it provides comprehensive advice for this stage.
Understanding puppy nutrition for healthy development
Growing puppies need more energy, protein and specific nutrients than adult dogs. Large and giant breed puppies should be fed a diet specifically formulated for their size - these contain less energy than small and medium breed puppy diets to support slower, controlled growth and protect developing joints. The most important thing is to stick with a complete and balanced puppy food and avoid adding supplements, particularly calcium, as imbalances can lead to abnormal bone growth.
A note on switching to adult food
Most puppies are ready to move from puppy food to adult food once they reach approximately 80% of their expected adult weight - generally 9 to 12 months for small breeds, around 12 to 15 months for medium breeds, and 15 to 24 months for large and giant breeds. The switch should be done gradually over 7 to 10 days to avoid stomach upset. For the full breakdown, including the day-by-day transition plan and how to choose the right adult diet, see our guide on switching from puppy to adult dog food.
For more information on feeding your puppy, take a look at:
Monitoring your puppy's growth and skeletal health
Skeletal Growth and Growth Plates
The size of a dog's skeleton is similar to the frame of a house in that it determines what size the dog will be when it is fully grown.
Bone growth
- The bones of small puppies stop growing around 6 months of age
- The bones of giant breed pups can still be growing up to 24 months of age
- Big bones and joints take a long time to develop and this is why large and giant breeds are often not fully grown until they are two years old
- Generally, most bone growth takes place between the ages of 4 to 8 months and, after this age, there is very little increase in the length of bones
Puppy growth plates
- Bone growth occurs in distinct areas of the bones which are called "growth plates"
- In long bones like the thigh bone, there is one growth plate at each end which allows the bone to lengthen as a puppy grows
- These growth plates are made from cartilage which is soft and flexible and thus prone to injury from trauma or overexercise
- Growth plates harden over time due to calcification - this is often called "growth plate closure"
- Once a growth plate has "closed", the bone can no longer grow
- In most breed, growth plates close around 12 months of age, however, the growth plates of large and giant breeds may stay open for longer
Assessing Growth Rate
The size of an adult dog is largely determined by the genes it has inherited from its mum and dad and feeding puppies to achieve a controlled growth rate will not affect their final adult body size.
Overfeeding puppies and making them grow too quickly can lead to orthopaedic issues like hip dysplasia and arthritis later in life.
Assessing your puppy's body condition score on a regular basis will help you determine if they are growing at the correct rate. These are the points to look for in a healthy pup:
- Ribs able to be felt without an excess fat covering
- Waist present behind the ribs when viewed from above
- Abdominal "tuck" present behind the ribs when viewed from the side
- Importance of regular veterinary check-ups during the growth phase
Regular vet check-ups during the growth phase let your vet monitor weight, body condition, and joint development, and catch issues like orthopaedic problems or dental abnormalities early. Your puppy will also need their full course of vaccinations during this period - see our puppy vaccinations schedule guide for the timing and what each shot covers.
Safe exercise practices for growing puppies
How do you burn up your puppy's seemingly boundless energy while still protecting their growing bones and joints?
Very young puppies
- Multiple short play sessions interspersed with puppy naps
- This approach will allow them to exercise their minds and bodies without becoming overtired
- This is also a good time to start teaching your puppy to walk on a lead at home
Fully vaccinated puppies
- When your puppy has finished their course of vaccinations and is confident walking on a lead, you can start to venture outside
- A good rule of thumb is to walk a puppy for five minutes for every month of their age. For example, you can walk a 6 month old puppy for 30 minutes once or twice daily.
Large breed puppies
- These puppies have a higher risk of developing joint problems when they are older
- Low impact exercise such as swimming, walking in water, and walking is a great way to promote muscle and bone growth while safeguarding cartilage and ligaments
- Small amounts of jumping and fast running is acceptable, but it shouldn't be your puppy's main form of exercise
- It is best to limit these high-impact activities until your puppy is at least 12 months of age
- Home activities that encourage healthy activity include toys that stimulate them mentally and physically, such as puzzle toys, tug of war, and hide and seek
For more information, read our article all about How Much Exercise Dogs Need.
FAQs
Navigating the puppy growth phase is a journey of rapid changes and exciting milestones. By tailoring your pup's nutrition, exercise, and veterinary care to their specific breed size and developmental stage, you are building a vital foundation for their future. Remember, every puppy grows at their own pace, so focus on maintaining a lean body condition and protecting those precious growing joints. Before you know it, your puppy will be a sturdy adult, ready for a lifetime of adventures by your side.
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History
Our experts continually monitor the health and wellness space and we update our articles when new information becomes available.
Wed 27 May 2026
Edited by Dr Gillian Hill BVSc (Hons)Dr Maree Monaghan BVSc (Hons)
Veterinarian
Dr. Maree graduated from the University of Queensland in 1990 with a Bachelor of Veterinary Science and has worked in a wide variety of practices around Australia and in Papua New Guinea. She has cared for all creatures great and small and has a particular interest in senior pets and horse nutrition
