What size collar for a Border Collie
Border Collies typically need a collar somewhere between 30 and 50cm in neck circumference, but the range is wide because the breed varies more in build than its consistent working appearance suggests — measuring your own dog's neck directly gives a far more reliable fit than picking a size from their weight alone.
Why measuring beats guessing from weight
Border Collies bred for working ability can vary noticeably in frame size even at a similar weight, with some running leaner and rangier and others stockier, and neck size does not scale perfectly with body weight across individual dogs. A collar bought purely off a breed-average size chart risks being too loose, which is a safety issue since a dog can back out of it, or too tight, which is uncomfortable and can rub.
Taking two minutes to measure your own dog properly avoids both problems and means you are choosing based on your actual dog rather than an average that may not apply to them specifically.
How to measure your Border Collie's neck
Wrap a soft tape measure around the base of your dog's neck, where a collar would naturally sit, snug enough that two fingers fit comfortably between the tape and their neck but no looser. Take the measurement with your dog standing normally rather than with their head lowered or turned, since neck circumference changes slightly with head position.
Add roughly 5cm to this measurement when choosing an adjustable collar's size range, to allow for a comfortable fit rather than buying to the exact number, which leaves no room for adjustment as a puppy grows or a working dog's neck muscles develop with training.
Checking the fit once it's on
The two-finger rule is the standard check: you should be able to slide two fingers flat between the collar and your dog's neck, but not much more. Too loose and an agile, athletic breed like a Border Collie can potentially back out of it, particularly one that pulls or startles; too tight and it can restrict comfort or rub over time.
Recheck the fit periodically, especially with a growing puppy or a dog whose build changes with fitness or age, since a collar that fit well six months ago is not guaranteed to still fit correctly now.
The sizes we stock
Everything below is in stock with us, priced with delivery worked out, and packed and posted by hand in the UK.
Real-Time GPS Pet Tracker
A compact GPS tracker that clips to most collars for real-time location, geofence alerts and find-me sound.
£29.99
MPS Medical PetS Boot – Waterproof Paw Protector
A vet-recommended waterproof boot that keeps bandages, dressings, and casts dry during walks and wet weather.
£30.49
Waterproof Dog Harness, Collar & Lead Set
A sturdy waterproof harness, collar and lead set that keeps walks tidy and your dog under control.
From£7.99
Remote Dog Training Collar with Handset
A remote training set pairing an adjustable receiver collar with a handheld controller. The LCD handset lets you select tone, vibration and static modes to reinforce recall and good behaviour from a distance.
£34.99
Common questions
- What size collar does a Border Collie puppy need?
- A puppy's neck grows quickly, so measure regularly rather than buying one collar expecting it to last, and choose an adjustable style with plenty of room to grow into rather than a fixed size. Check the fit every few weeks during their main growth period.
- How do I know if a collar is too loose?
- If you can fit more than two fingers comfortably between the collar and your dog's neck, or if your dog has ever slipped a collar off, it is too loose. An agile, athletic breed like a Border Collie is particularly capable of backing out of a loose-fitting collar.
- Should a Border Collie wear a collar all the time?
- Many owners keep a well-fitted collar on for identification purposes, but check local guidance and your dog's comfort, and some owners remove it during unsupervised periods at home to reduce any snagging risk. A well-fitted, breakaway-style collar reduces this risk if you do keep it on.
Sources
Written against guidance published by UK veterinary and welfare organisations. Always confirm specifics with your own vet.
Written by Matt Garnett, who runs Giddy Pets and is a lifelong pet owner — not a vet. This is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your animal. How we write these guides.