Getting your dog's collar size wrong is more common than you'd think — and more of a problem than most owners realise. A collar that's too tight restricts breathing and can cause pressure sores. One that's too loose can slip off mid-walk, or your dog can get a paw caught underneath it.
The fix is simple. Measuring properly takes about 30 seconds and prevents all of this. Here's exactly how to do it.
What You'll Need
Just two things: a soft measuring tape (the kind used for sewing) and a steady dog.
If you don't have a soft tape, a piece of string and a ruler work perfectly well. Wrap the string, mark where it meets, then measure the length with a ruler.
Do not use a rigid tape measure. It doesn't flex around the curve of your dog's neck and will give you an inaccurate reading — usually too large, which means a collar that's too loose.
How to Measure Your Dog's Neck — Step by Step
Step 1: Position your dog standing
Have your dog stand on all four paws. Sitting changes the natural position of the neck and can affect the measurement by up to 2–3 cm in larger breeds. If your dog won't stay still, have someone help or use a handful of treats.
Step 2: Find the right spot
Measure around the base of the neck — roughly where the collar would naturally sit, about 5 cm down from the base of the skull. Don't measure at the narrowest point just below the head. Collars don't sit there, and measuring there will give you a collar that's too tight around where it actually sits.
Step 3: Take the measurement
Wrap the tape around the neck snugly but not tightly. Read the number in centimetres.
Step 4: Apply the 2-finger rule
Slide two fingers flat under the tape. If they fit comfortably with a little room to spare, you have the right measurement. If it's tight with two fingers, add 1 cm. If you can fit three fingers easily, subtract 1 cm.
This final number is your collar size.
The 2-Finger Rule Explained
The 2-finger rule is the standard used by professional dog trainers and recommended by the British Veterinary Association (BVA). It ensures the collar is firm enough to stay on but loose enough that your dog can breathe, swallow, and move their head comfortably.
One finger means too tight. Three fingers means too loose — particularly risky for escape artists like Whippets, Beagles, and any dog who's learned to back out of their collar.
Dog Collar Size Chart by Breed
These are starting points only. Always measure your own dog — neck size varies significantly even within the same breed.
| Breed | Typical neck size |
|---|---|
| Chihuahua, Toy Poodle | 18–25 cm |
| French Bulldog, Pug, Shih Tzu | 28–38 cm |
| Cocker Spaniel, Beagle | 32–42 cm |
| Border Collie, Dalmatian | 38–48 cm |
| Labrador, Golden Retriever | 42–55 cm |
| German Shepherd, Dobermann | 45–58 cm |
| Great Dane, Rottweiler, Newfoundland | 55–70 cm |
| Greyhound, Whippet, Lurcher | 32–42 cm (wide collar required — see below) |
Note: Brachycephalic breeds (French Bulldogs, English Bulldogs, Pugs) often have necks that are thick relative to their body size. Weight alone is a poor predictor. Always measure.
Special Cases: Puppies, Fluffy Breeds, and Sighthounds
Puppies
Puppies grow fast — faster than most owners expect. A collar that fits perfectly at 8 weeks can be dangerously tight by week 16. Measure monthly for the first 6 months, then every 2–3 months until your dog is fully grown. If you ever notice the collar leaving marks in the fur or your puppy scratching at it more than usual, check the fit immediately.
Fluffy or double-coated breeds
For breeds with thick coats (Husky, Samoyed, Golden Retriever, Chow Chow), part the fur and measure the circumference of the neck itself — not the outer surface of the coat. Collars sit against the skin and the undercoat, not on top of the outer fur. Measuring over the coat will give you a reading that's too large.
Sighthounds (Greyhound, Whippet, Lurcher, Saluki)
Sighthounds are the exception to standard sizing. Their necks are wider than their skulls, which means a regular collar sized to the neck measurement will simply slip over their head when they pull back. They need either a wide martingale collar or a custom-fitted collar measured specifically to the widest point of the neck — which is typically 2–3 cm higher than where a normal collar sits. For sighthounds, measure both the narrow point (base of neck) and the wide point (just below the skull), and use the larger measurement when choosing a martingale.
How to Check If an Existing Collar Fits
Already have a collar on your dog? Run through these checks:
Too tight:
- You cannot fit two fingers comfortably under the collar
- The collar leaves indentations in the fur or marks on the skin
- Your dog scratches at it frequently or shakes their head
Too loose:
- Three or more fingers fit easily underneath
- The collar shifts or rotates on its own throughout the day
- Your dog can back out of it by pulling their head backwards
Just right:
- Two fingers fit snugly with a small amount of give
- The collar stays centred without rotating
- Your dog shows no awareness of it
The BVA recommends checking your dog's collar fit every few weeks — particularly for puppies still growing, and for dogs whose weight fluctuates seasonally.
Ready to Choose a Collar?
Once you have your measurement, look for a collar where that measurement falls comfortably in the middle of the adjustment range — not at either extreme. A collar used at its tightest or loosest hole has no room for adjustment if your dog's neck changes.
If you're between two sizes, always size up and use the buckle to tighten.
Our leather collars are available in sizes covering 25–70 cm with precise adjustment in small increments. Each product page lists the full adjustment range so you can match it to your measurement before you buy.
Frequently Asked Questions
What if my dog's neck measurement falls between two sizes?
Size up and use the buckle to bring it in. A collar used at its absolute tightest leaves no room for a bad hair day — or a well-fed Christmas.
Should I measure before buying every new collar?
Yes, even if you know your dog's "size." Adjustment ranges, buckle positions, and collar widths vary between brands and styles. A 42 cm collar from one maker may have a completely different usable range to a 42 cm collar from another.
Can I use a piece of string instead of a tape measure?
Absolutely. Wrap string around the neck, mark the overlap point, lay it flat and measure with a ruler. Add 2–3 cm for the 2-finger allowance and you have your collar size.
My dog hates being touched around the neck — how do I measure?
Work slowly and pair every moment of contact with high-value treats. If your dog is genuinely collar-averse or panics when anything goes near their neck, speak to your vet or a qualified clinical animal behaviourist. There may be an underlying sensitivity or a past negative association worth addressing — especially before fitting any collar.
How often should I check collar fit?
Monthly for puppies under 12 months. Every 3–6 months for adults, or whenever your dog's weight changes noticeably.
It Takes 30 Seconds — Do It Before You Buy
Measuring your dog's neck is the smallest step that makes the biggest difference to their comfort and safety. The 2-finger rule is all you need to know. Measure, apply the rule, and choose a collar with an adjustment range that puts your measurement comfortably in the middle.
Not sure which collar style is right for your dog? Browse our full collar collection, or read our guide on collar matterials, and harnesses to find the best fit for your dog's breed and behaviour.