How to measure a dog for a collar
A well-fitting collar sits snug enough that it will not slip over your dog's head, but loose enough to fit two flat fingers comfortably between the collar and the neck. To measure, wrap a soft tape measure around the base of your dog's neck, where a collar would naturally sit, and add a small allowance for that finger-width gap.
Taking the measurement properly
Use a soft fabric tape measure rather than a rigid ruler, and wrap it around the base of the neck, roughly where an existing collar sits or would naturally sit, rather than higher up near the jaw or lower down at the shoulders. Keep the tape snug but not tight, following the natural curve of the neck rather than pulling it straight, since a straight-line measurement will read shorter than the actual circumference.
It helps to measure while your dog is standing in a relaxed, natural position rather than sitting or straining against a lead, since posture can genuinely change the neck measurement by a noticeable amount. If you do not have a soft tape measure to hand, a piece of string or ribbon wrapped around the neck and then measured flat against a ruler works just as well.
Getting the fit right, not just the size
Once you have the base measurement, the two-finger test is the practical way to judge fit: with the collar fastened, you should be able to slide two flat fingers snugly between the collar and your dog's neck, but not much more room than that. Too loose and a collar risks slipping over the head, particularly for narrow-headed breeds like Greyhounds and Whippets; too tight and it can rub, restrict breathing, or cause discomfort with movement.
Coat thickness matters here too — a dog with a dense, fluffy coat may need the collar checked with the coat settled naturally rather than fluffed up, since a collar that looks loose over thick fur can actually be quite snug against the skin underneath once the coat lies flat.
Rechecking fit as your dog changes
A growing puppy needs their collar fit checked regularly, sometimes as often as every couple of weeks during a fast growth spurt, since a collar that fitted well a month ago can become dangerously tight without an obvious warning sign beyond the collar simply looking snugger than before. Adult dogs are far less likely to need frequent rechecks, but weight changes, either gain or loss, are worth a quick two-finger check whenever you notice them.
It is worth getting into the habit of running the two-finger test occasionally even on a collar that has fitted well for a long time, particularly through a season where your dog's coat thickness changes considerably, since what felt right in a thin summer coat can sit differently once a thicker winter coat grows in underneath it.
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
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
Smart Bluetooth Tracker Tag (Works with Find My)
A compact Bluetooth tracker that pairs with Apple Find My for global positioning, with left-behind alerts and the option to share tracking with up to six people. Clip it to a pet collar, keys or bag so nothing goes missing.
From£7.99
Flea & Tick Repellent Collar for Dogs & Cats
An adjustable 70cm repellent collar, water-resistant and trimmed to fit either a cat or a dog, giving day-to-day deterrence against fleas and ticks with no drops to apply.
£7.99
Common questions
- How do I know if my dog's collar is too tight?
- If you cannot comfortably fit two flat fingers between the collar and your dog's neck, it is likely too tight. Watch also for rubbing, hair loss under the collar, or your dog pawing at it, all of which can indicate discomfort even if the two-finger test seems borderline.
- How often should I check my puppy's collar fits?
- Roughly every couple of weeks during a fast growth period is a sensible habit, since a collar can go from comfortable to dangerously tight surprisingly quickly during a growth spurt without any obvious sign other than the fit itself changing.
- Should I measure my dog's neck with or without their fur fluffed up?
- Measure and check fit with the coat settled naturally rather than fluffed, particularly for thick or fluffy coats, since a collar that appears loose over puffed-up fur can actually sit quite snug against the skin once the coat lies flat.
- What's the risk of a collar that's too loose?
- A collar that is too loose can slip over your dog's head, which is a particular risk for narrow-headed breeds such as Greyhounds and Whippets, and it also gives less control if your dog pulls on the lead. The two-finger test helps find the right middle ground.
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.