Most adult Border Collies grow to about 18–22 inches tall and weigh 30–55 pounds, depending on gender and genetics.
Wondering how big your Border Collie will get? You’re not alone. Size can affect your dog’s health, diet, space needs, and more. Many new Border Collie owners are surprised by how fast their pup grows—and how much space this energetic breed really needs. The good news? Border Collie growth follows clear stages, and with a little guidance, it’s easy to understand what to expect. In this article, you’ll learn exactly how big Border Collies get, how fast they grow, and what factors can change their size. Let’s explore it all step by step—with charts, expert tips, and real-life examples.
Average Size of a Full-Grown Border Collie
Typical Height and Weight (Male vs Female)
Most adult Border Collies fall into a medium-sized dog category. Their size depends on gender, genetics, and whether they come from a working or show line.
Male Border Collies are usually 19–22 inches tall at the shoulder and weigh 40–55 pounds.
Female Border Collies are slightly smaller, typically 18–21 inches tall and weigh 30–45 pounds.
Border Collies have a lean, athletic build. They are made for movement and agility. Their weight should match their activity level and frame. You can check your dog’s growth against the American Kennel Club (AKC) breed standard, which offers more size and structure info.
Differences in Working Line vs Show Line Border Collies
Border Collies bred for work often look different from those bred for shows. Working-line dogs are lighter and more muscular, built for stamina and speed. Show-line Border Collies may be stockier with thicker coats and slightly more mass.
While both types fall in the same size range, working dogs tend to stay on the lower end of the weight scale. If your dog comes from strong herding bloodlines, don’t worry if they’re lean—they’re built for performance.
Border Collie Size Chart
Here’s a helpful growth chart to give you an idea of how your Border Collie might develop:
| Age | Male Height (inches) | Female Height (inches) | Male Weight (lbs) | Female Weight (lbs) |
|---|---|---|---|---|
| 8 weeks | 8–10 | 7–9 | 5–8 | 4–7 |
| 3 months | 10–12 | 9–11 | 12–15 | 10–13 |
| 6 months | 14–18 | 13–16 | 20–30 | 18–25 |
| 9 months | 18–21 | 17–20 | 30–45 | 25–35 |
| 12 months | 19–22 | 18–21 | 35–55 | 30–45 |
Keep in mind that individual dogs may grow faster or slower. Some finish growing by 12 months, others take up to 18 months or longer.
Border Collie Growth Stages
Puppy Stage (0–6 months)
Border Collie puppies grow fast during the first few months. Their bones, muscles, and joints are developing quickly. This is when they double and even triple in size. During this stage, they are full of energy and may be clumsy as they learn to control their growing bodies.
Make sure your puppy gets enough food and rest. Veterinary nutritionists recommend feeding a balanced puppy diet to support strong bone and joint growth.
Adolescent Stage (6–12 months)
This stage is often called the “teenage phase.” Growth slows a bit, but your Border Collie still has plenty of filling out to do. They may go through growth spurts, and some dogs look lanky or out of proportion.
You’ll also see more behavioral changes at this age. They’ll need clear training, social time, and lots of exercise. Good habits now will help them become calm, confident adults.
Adult Stage (12–24 months)
Most Border Collies reach full height by 12 months, but they keep gaining muscle and body mass until about 18–24 months. This phase is when their adult look fully forms—thicker fur, stronger frame, and more defined muscles.
Diet and activity levels make a big difference here. Active dogs tend to be leaner. Dogs with less exercise may put on extra weight, which can lead to joint strain or health issues. Keep up with vet visits to monitor your dog’s body condition score (BCS) and adjust as needed.
When Do Border Collies Stop Growing?
Most Border Collies stop growing in height by 12 to 15 months but may continue filling out until 18 to 24 months. The growth timeline varies by genetics, gender, and health. If your dog seems unusually small or large, check with your vet to rule out any growth issues or nutritional gaps.
Factors That Influence Border Collie Size
Genetics and Lineage
Genetics is the #1 factor that determines size. If your Border Collie’s parents were small, chances are your pup will be too. Pedigree records can offer helpful clues.
Dogs from a working background may be smaller and leaner. Those from show lines may grow slightly larger, especially in body mass and coat density.
Diet and Nutrition
Nutrition has a big impact on healthy growth. Puppies need balanced meals with the right amount of protein, fat, and vitamins. Feeding too little or too much can cause poor growth or weight problems.
Avoid overfeeding large portions or high-calorie treats. Ask your vet or refer to WSAVA nutritional guidelines for proper feeding practices based on age and size.
Exercise and Activity Level
Active Border Collies tend to stay lean and well-toned. Daily movement helps develop muscles and keeps bones strong. But too much intense play before their joints fully mature (under 12 months) can harm development.
Use age-appropriate games like short walks, gentle fetch, or puzzle toys to build strength without pressure on growing joints.
Neutering/Spaying and Growth Impact
Early neutering can affect a dog’s growth. It often causes the growth plates to stay open longer, leading to taller adult dogs with a lankier frame. Some studies suggest this may increase the risk of joint issues in large or active breeds.
Talk to your vet about the best age for neutering or spaying your Border Collie, especially if your dog is working or highly active.
How to Tell If Your Border Collie Is a Healthy Size
Signs of Underweight or Overweight
It’s easy to miss changes in your dog’s weight. That’s why it’s important to know what signs to look for.
If your Border Collie is underweight, you may see:
- Visible ribs, spine, or hip bones
- Low energy or weakness
- Dull or thinning coat
If your dog is overweight, you might notice:
- Little to no waistline
- Heavy breathing after short walks
- Trouble moving or jumping
Use your hands to feel their sides. You should be able to feel ribs without pressing hard, but they should not be sticking out. If you’re unsure, your vet can do a quick check during regular visits. You can also compare your dog’s look to body condition score (BCS) charts created by vets.
Ideal Body Condition Score
A healthy Border Collie usually scores a 4 or 5 out of 9 on a body condition chart. This means:
- You can feel the ribs, but they’re not visible.
- Your dog has a waist when viewed from above.
- There’s a slight tummy tuck when viewed from the side.
This system helps owners and vets track if a dog’s weight is in a safe range. Staying at a healthy weight lowers the risk of joint problems, heart disease, and diabetes. You can learn more about BCS on trusted vet sites like VCA Hospitals.
When to Consult a Vet
If your Border Collie gains or loses weight quickly, speak with your vet. Sudden changes may point to health problems such as thyroid issues or digestive troubles.
It’s also a good idea to ask for weight guidance at each check-up. Your vet can weigh your dog, check muscle tone, and adjust feeding or exercise plans. This is especially helpful for active or aging dogs whose needs change with time.
Comparing Border Collie Size to Other Dog Breeds
Are Border Collies Medium or Large Dogs?
Border Collies are considered medium-sized dogs, though they’re on the higher end of the scale. They’re bigger than small breeds like Beagles, but smaller than large dogs like Golden Retrievers.
Their lean shape can make them appear smaller than they are. But don’t let that fool you—Border Collies need room to run and burn energy every day. Their size and energy level make them best suited for homes with yards or active families.
The American Kennel Club lists them in the “herding group,” where they sit in the mid-range for both height and weight.
Border Collie vs Australian Shepherd vs Labrador
Here’s how Border Collies compare to two popular breeds:
| Breed | Average Height (inches) | Average Weight (lbs) | Energy Level | Build |
|---|---|---|---|---|
| Border Collie | 18–22 | 30–55 | Very High | Lean, athletic |
| Australian Shepherd | 18–23 | 40–65 | High | Stocky, muscular |
| Labrador Retriever | 21–24 | 55–80 | Moderate-High | Broad, solid |
As shown above, Border Collies are slimmer and often more energetic than the others. Labs are heavier and more relaxed, while Australian Shepherds fall somewhere in between. Choosing the right breed for your home often depends on space, time, and activity level.
Common Questions About Border Collie Size
Do Male Border Collies Get Bigger Than Females?
Yes, in most cases. Male Border Collies tend to be both taller and heavier than females by a few inches and pounds. Males also often have a broader chest and thicker neck.
Still, individual dogs vary. Some females may grow larger than smaller males. Genetics, nutrition, and exercise all play a role in size.
Is There Such a Thing as a Mini Border Collie?
Technically, there’s no official mini Border Collie breed. However, some breeders offer smaller-sized Border Collies through selective breeding. These dogs may be crossbred with smaller breeds to reduce size.
Be cautious—so-called “mini” Border Collies may have health risks or unpredictable behavior due to mixed genetics. It’s best to adopt from a reputable breeder or rescue group that prioritizes health and temperament over size.
How Big Will My Border Collie Puppy Get?
The best way to estimate your puppy’s adult size is by checking the size of their parents. Most Border Collies reach 50% of their adult weight by 4 months and nearly full size by 12 months.
Here’s a quick formula many vets use:
Adult weight ≈ (Puppy weight at 14 weeks) × 2
You can also ask your vet for growth tracking help. They’ll watch for healthy weight gain and let you know if your pup is growing too fast or too slow.
Conclusion
Border Collies are smart, active, and medium-sized dogs. Most full-grown males weigh between 35–55 pounds, while females range from 30–45 pounds. Their height usually falls between 18 and 22 inches at the shoulder.
Size depends on things like genetics, diet, exercise, and overall health. Some may grow larger or smaller than the average, especially if they’re mixed breed.
To keep your Border Collie healthy, check their body shape often. Look for signs of being too thin or overweight. Your vet can help guide you with the right food and activity plans.
Whether you’re raising a pup or adopting an adult, knowing how big Border Collies get helps you prepare your home, training, and lifestyle to match their needs. A well-cared-for Border Collie will return that effort with love, loyalty, and lots of tail wags.