What size collar does my puppy need?

Measure your puppy's neck the same way you would an adult dog, then check back every few weeks while they are growing rather than buying once and assuming it still fits. Many owners find they need to move up a size, or loosen an adjustable collar, several times before their dog is fully grown.

How do I know if a collar is too tight?

You should be able to fit two fingers flat between the collar and your dog's neck. If you can only manage one finger, or the collar leaves a visible line in the fur when removed, it is too tight and needs loosening or sizing up.

How do I know if a collar is too loose?

If you can slide more than two fingers underneath it, or your dog has ever managed to back out of it during a walk, the collar is too loose. A collar your dog can slip over their head is not doing its job in an emergency.

Should I measure over my dog's fur or against the skin?

Measure over the fur as it normally sits, since that is how the collar will actually sit day to day. There is no need to part thick or long coats to measure against the skin underneath, and doing so usually gives a tighter reading than the collar will actually experience.

How to measure your dog for a collar

Measuring your dog is the only reliable way to get a collar that fits, and it takes two minutes with a soft tape measure or a length of string. The right collar sits snugly enough that it cannot slip over your dog's head, with room for two fingers to fit flat between the collar and the neck — not looser, and not tighter.

Measuring your dog's neck

Wrap a soft tape measure, or a piece of string you then measure against a ruler, around the base of your dog's neck where a collar would normally sit — not up near the ears, and not right down at the shoulders. Keep the tape flat against the fur rather than pulling it into the coat, and take the measurement while your dog is standing normally rather than sitting or straining.

Slide two fingers flat underneath the tape as you measure, so the final number already allows for that gap rather than needing you to add it on afterwards. If your dog wriggles, measure twice and use the larger of the two readings — a collar that is a fraction loose is safer than one that is a fraction tight.

Reading the size on the label

Most collars are sold by a size range in centimetres, such as 30–40cm or 40–50cm, printed on the label or the product page. Your measurement needs to fall comfortably within that range rather than right at one end of it, because most collars are adjustable across only part of the stated range.

If your dog's neck measurement sits right on the boundary between two sizes, go with the larger one and adjust it down. A collar that is too small to do up properly is far more of a problem than one with a little spare adjustment left over.

Getting the fit right

The two-finger rule is the standard check once the collar is on: you should be able to slide two fingers flat underneath it, but not a whole hand. Too loose and a determined or frightened dog can back out of it; too tight and it will rub, particularly on a short-coated breed.

Puppies and dogs who are still growing need their collar checked every few weeks rather than fitted once and forgotten, since a snug fit in spring can be uncomfortably tight by autumn. Recheck the fit any time your dog's weight changes noticeably, too.

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

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Common questions

What size collar does my puppy need?: Measure your puppy's neck the same way you would an adult dog, then check back every few weeks while they are growing rather than buying once and assuming it still fits. Many owners find they need to move up a size, or loosen an adjustable collar, several times before their dog is fully grown.
How do I know if a collar is too tight?: You should be able to fit two fingers flat between the collar and your dog's neck. If you can only manage one finger, or the collar leaves a visible line in the fur when removed, it is too tight and needs loosening or sizing up.
How do I know if a collar is too loose?: If you can slide more than two fingers underneath it, or your dog has ever managed to back out of it during a walk, the collar is too loose. A collar your dog can slip over their head is not doing its job in an emergency.
Should I measure over my dog's fur or against the skin?: Measure over the fur as it normally sits, since that is how the collar will actually sit day to day. There is no need to part thick or long coats to measure against the skin underneath, and doing so usually gives a tighter reading than the collar will actually experience.

Sources

Written against guidance published by UK veterinary and welfare organisations. Always confirm specifics with your own vet.

Blue Cross — Pet advice

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.