How big does a Border Collie get?
A full-grown Border Collie is a medium dog, weighing about 30–55 lb as an adult.
- Adult weight
- 30–55 lb
- Also in kilograms
- 13.6–24.9 kg
- Size class
- Medium
As a medium breed, a Border Collie reaches its adult weight earlier than a large dog — smaller breeds finish growing sooner (Hawthorne et al., 2004).
Common questions
How much does a full-grown Border Collie weigh?
A Border Collie weighs 30–55 lb (13.6–24.9 kg) as an adult. That range is the weight the American Kennel Club publishes in the breed's official standard, re-checked here every week — it is a typical weight across many adult dogs, not a target for one dog.
Is a Border Collie a medium dog?
Yes — a Border Collie counts as a medium breed, going by the middle of its adult weight range (13.6–24.9 kg). The cut-offs between small, medium, large and giant are a common veterinary convention rather than one official standard, so a breed near a boundary can be described either way elsewhere.
When does a Border Collie stop growing?
Earlier than a large dog. Hawthorne et al. (2004) measured that smaller breeds finish growing sooner, so a Border Collie reaches something close to its adult weight before a big breed would. We don't publish a month-by-month figure, because no source gives one breed by breed — and an invented number would be worse than none.
Why is there a range instead of one weight?
Because the source publishes a range. Within any breed, weight varies with sex, genetics, build and health, and a mixed-breed dog usually falls between its parents' breeds. Narrowing 30–55 lb down to a single number would look more precise while being less true.
Breeds of a similar size
Weight varies within the Border Collie by sex, genetics and health, and mixed-breed dogs fall between their parents. This is a typical range, not a guarantee.
Verified on . Based on Breed weights — official AKC breed standards (American Kennel Club, breed pages, accessed 2026-07-29) and Body-Weight Changes during Growth in Puppies of Different Breeds (Hawthorne et al., Journal of Nutrition, 2004, vol. 134, p. 2027S). See the method.