When Do Border Collies Stop Growing

When Do Border Collies Stop Growing?

Border Collies are one of the most popular dog breeds on the planet. They’re known for their beautiful coats, their high-energy personalities, incredible herding talents, and of course, their superior intelligence.

If you are thinking of getting a Border Collie puppy you may be wondering when Border Collies stop growing?

Every Border Collie is a little different, but the majority of Border Collies will reach their full adult size by 15 months old.

Let’s take a look a Border Collie’s growth in more detail!

How Big Will My Border Collie Get?

The average adult male Border Collie is 19-22 inches (48-56 cm) tall and weighs 30-44 lbs (14-20 kgs), while the average female tends to be a little bit smaller at 18-20 inches (46-53 cm) tall and lighter at 26-41 lbs (12-19 kgs).

Your Collie’s exact size will depend on their genetics, diet, and activity level.

They are an incredibly active breed and have an athletic build to match, with long bodies and lean muscles. To ensure your Collie maintains a healthy weight for their size, it’s essential that they eat a good diet and get at least two hours of exercise a day.

Stages Of Border Collie Growth

The key stages of Border Collie development are newborn, juvenile, adolescent, and adult.


Border Collies typically weigh somewhere between 7-14 ounces at birth, and for the first few weeks of life, they should only be fed their mother’s milk, which contains all of the key nutrients they need to start developing their little bones, senses, and minds.

At 3-4 weeks of age, they can start to be weaned off of their mother’s milk and gradually transition to high-quality solid food for puppies.

By this time, they will be walking, vocalizing, teething, and even starting to run and play.


By 8-10 weeks, they should be eating only solid food. At this stage, puppies are considered juveniles and will be learning, exploring, socializing, and causing lots of mayhem.

To continue growing at a healthy rate, they should be eating 20kg per 1kg of their body weight per day, and gaining up to 10% of their body weight per week.

They should also be eating 3-4 small meals per day as to not overwhelm their metabolism. It is essential that your pup eats food tailored to their age group, as they contain all of the key nutrients their bodies and brains need to develop.


At 6 months old, your Collie will enter adolescence and they will start to regulate their energy levels just a little bit.

At this stage, they can finally drop down to two bigger meals per day, which they should continue with for the rest of their lives. You may also want to switch to food for juniors, although lots of owners just continue with puppy food.


Finally, at 12 months old, your Collie is physically considered an adult, and they should be transitioned gradually to adult food.

Although they continue to fill out and develop until 15 months, most Collies will have reached their adult height by 12 months old.

Your Collie should eat adult food until they are considered seniors at 7-8 years of age, and then they should transition to senior food.

As with puppies, it is essential that senior dogs eat food that is tailored to their age group for bodily and cognitive support.

Diet Of A Growing Border Collie

Growing Collies need to eat high-quality foods that are nutritiously complete with high protein content (at least 25%).

They need to eat lean meats like chicken and salmon to power their active muscles, as well as healthy fats from Omega fatty acids, (especially DHA and EPA), to support their developing bones and minds.

Key vitamins include vitamins A, B, C, D, E, and K and essential minerals include calcium and magnesium. Your pup’s food should also contain healthy carbohydrates like rice for energy and anti-oxidants for protective health.

Always opt for foods that are made using natural ingredients and avoid those containing filler ingredients and artificial additives.

If your pup is sensitive, you should also avoid foods containing allergens like gluten and opt for those containing hypoallergenic ingredients with added probiotics.

When Do Border Collies Mature?

In terms of sexual maturity, Border Collies will become sexually mature and able to reproduce between 6-12 months of age.

Female Collies usually experience their first heat cycle at or after 6 months old, and males tend to reach sexual maturity at around 7 months old.

However, it can take up to a year for both sexes, and it’s not recommended that dogs under 1 (preferably 2) years old are used for breeding, especially females. This is because they are still adolescents and they are still developing in other ways.

Mental maturity can take a little longer in Border Collies than in many other dogs. Most medium-sized breeds take between 12 and 18 months to mature, but the brighter the dog, the longer it takes, and Collies are the brightest breed of all.

It varies from dog to dog, but it typically takes between 2-3 years for Border Collies to mentally and emotionally mature.

That said, it is a gradual process, and although your Collie will always be active, they will learn to regulate their energy levels slowly over their first few years.


Border Collies generally reach their full adult size by 15 months old but take longer to finish fully developing mentally. A Border Collie will be around 2 or 3 years of age before being mentally and emotionally mature.

All in all, Border Collies are fantastic high-energy dogs to own, that will give you many years of fun antics even after they are fully grown.