How to Measure a Dog for a Collar (and Check the Fit)

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A collar that fits well stays on when your dog pulls back, does not press on the throat, and does not rub the coat away. Getting there takes two things: a neck measurement to pick the right size, and a fit check once the collar is on. This guide covers both, plus the extra checks for puppies, dogs with narrow heads, and ID tags.

How we wrote this: the fit advice comes from Whole Dog Journal (articles by trainer Pat Miller and founding editor Nancy Kerns), the UK rescue charity Battersea Dogs and Cats Home and Best Friends Animal Society, all checked on 1 November 2026. Size ranges come from maker pages already cited on our product pages. We did not test these collars ourselves, and we do not show prices or ratings.

What you need

• A soft tape measure, the kind used for sewing. If you only have a rigid tape, wrap a piece of string around the neck, mark it, and measure the string flat.
• Your dog’s current collar, if it fits well. Its length at the hole you use is a useful cross check.
• The size chart for the collar you plan to buy. Sizes are not standard between brands, so the maker’s chart is the one that counts.
• Something your dog likes, such as a toy or praise, to keep the session calm.

How to measure a dog for a collar, step by step

Step 1: Find where the collar sits

A flat collar sits around the middle of the neck, below the head and above the shoulders. Run your hand down from the back of the skull: the collar belongs on the neck itself, not up against the ears and not sliding down onto the chest. Measure your dog standing up, with the head in a normal position, because a lowered or raised head changes the number.

Step 2: Measure the neck

Wrap the tape around the neck at that spot. Keep it flat against the coat, not pulled tight into the fur and not hanging loose. Read the number where the tape meets its start. On a fluffy dog, press gently enough that you are measuring the neck under the coat rather than the hair on top of it.

Step 3: Add room for the two-finger fit

The fit check that Whole Dog Journal and Battersea both describe is two fingers between collar and neck (more on that below). So the size you buy should let the collar close at your dog’s neck measurement plus about two fingers of room. In practice, slide two fingers flat under the tape and read the number again; that is the length you want the collar to close at.

Step 4: Pick a size where you land in the middle

Collar sizes are ranges, not single numbers, and they differ by brand. For example, the maker lists the Ruffwear Front Range collar in neck ranges of 11 to 14, 14 to 20 and 20 to 26 inches, the small Blueberry Pet Classic nylon collar fits 12 to 16 inches, and the EzyDog Neo Classic Wide starts at 18 to 21 inches for size L. If your number falls in the middle of a range, you have room to adjust both ways. If it sits right at the top of one size, the next size up usually gives a better fit, but check the maker’s own advice first, since some say to size down.

Step 5: Fit the collar and do the two-finger check

Put the collar on, close it, and slide two fingers flat between the collar and your dog’s neck. Whole Dog Journal says a properly fitted flat collar lets you slip two fingers under it, held at right angles to the neck. Battersea gives the same rule and says the collar should fit snugly. If you cannot get two fingers in, loosen it a notch. If you can fit three or the collar slides easily up toward the ears, tighten it.

Step 6: Check it again after a walk

A collar can shift once your dog shakes, runs or pulls. After the first walk, check that it is still in the middle of the neck, that the fit is still two fingers, and that there is no rubbing or flattened fur. Whole Dog Journal notes that a well made collar should lie evenly around the neck without pressing or bending inward in a way that could rub, and that some materials can wear bare patches on dogs with very thin coats; it suggests a fleece lined collar for those dogs.

Neck size vs head size: when two fingers is too loose

The two-finger rule assumes your dog’s head is wider than the neck, so the collar cannot slip off over the ears. That is not true for every dog. Whole Dog Journal explains that slender skulled sighthounds such as Greyhounds, and thick necked breeds such as Pugs, often have heads not much wider than their necks, and a two-finger gap lets them back out of the collar and get loose.

For these dogs, the same article suggests a limited slip (martingale) collar. It tightens when the leash is pulled, but only up to a set point. WDJ says the aim is a collar that is loose enough to be comfortable, tight enough under tension that the dog cannot slip out, and never tight enough at its smallest to choke. To fit one, adjust it so that when the loop is pulled fully closed it is snug around the neck but still not tight. Because these collars tighten, WDJ says not to leave them on a dog who is left alone or playing with other dogs.

A quick test for any dog: with the collar on, gently pull it forward toward the ears. If it slides over the head easily, it is too loose for that dog, whatever the finger test says.

Measuring a puppy for a collar

Puppies need the same measurement and the same two-finger fit, but they will not keep it for long. Battersea says puppies, and dogs who need to gain weight, can outgrow a collar very quickly, and that if a puppy keeps scratching at a new collar you should check the fit. Some scratching or mouthing at first is normal, Battersea adds, because a collar is a new feeling.

• Check the fit often. Make the two-finger check part of your routine while your puppy is growing, for example every time you clip on the leash.
• Buy for adjustment, not for growth. Pick a collar whose range has room above your puppy’s current neck size, but that still closes snugly today. A collar that is too big now can slip off.
• Be gentle on the neck. Whole Dog Journal warns that even a flat collar can hurt a puppy’s soft windpipe if the puppy pulls, so puppies that pull may be better walked on a harness. See how to measure a dog for a harness.

To help your puppy get used to the collar, Battersea suggests letting them sniff it first, rewarding calm interest, putting it on in small steps, and slowly building up how long it stays on. If your dog freezes, panics or growls, it says to stop and get help, and to speak to your vet if you see signs of pain.

ID tags and the collar

A well fitted collar is also where your dog’s ID lives. Best Friends Animal Society says your dog should always wear a current ID tag on the collar, so you can be called if your dog is found, and should have a microchip too. Its microchip guide explains why both matter: whoever finds your dog may not have a microchip scanner, but anyone can read a tag. Whole Dog Journal adds a simple habit: check that the phone number on the tag is still current, and that the microchip is registered with your current details. In the UK, Battersea notes, dogs must wear a collar and ID tag with the owner’s name and address in public.

Two tag tips from Whole Dog Journal: on small dogs, a tiny collar ring can make it hard to attach both a leash and a tag, and you can tape tags flat to the collar or use a tag pocket so they do not dangle. And if you leave a collar on during play with other dogs, it suggests a quick release buckle or, better, a breakaway safety collar that opens under pressure.

Signs the collar does not fit

• Too tight: you cannot get two fingers under it, it leaves a dent in the fur, or you see rubbed or bare patches. Loosen it and check the skin. If the skin is sore, see your vet.
• Too loose: you can fit more than two fingers, it slides up over the ears when you pull it forward, or it turns all the way round so the buckle sits under the chin.
• Wrong style: your dog backs out of a correctly fitted flat collar. Look at a martingale collar, as WDJ suggests above, or a harness.
• Discomfort: Battersea says a dog who is reluctant to walk may be wearing a collar, lead or harness that is uncomfortable or poorly fitted, so check fit before you assume it is a training problem.

Is your dog wearing ID? See what to put on a dog ID tag: what to engrave, which tag type to pick and why a tag and microchip work together.

New puppy? See how to get a puppy used to a collar and leash: short steps at home, leash biting, and planning the first walks.

FAQ

How tight should a dog collar be?

Snug, with room for two fingers held flat between the collar and the neck. Whole Dog Journal and Battersea both use this rule, and Battersea says the collar should fit snugly.

How do I measure my dog’s neck for a collar?

Wrap a soft tape measure around the middle of the neck, where the collar sits, with your dog standing. Keep the tape flat, then slide two fingers under it to see the length the collar should close at. Compare that with the maker’s size chart.

Should I size up or down between collar sizes?

Choose the size that puts your measurement in the middle of its range, so you can adjust both ways. Makers differ, so follow the advice on the size chart of the collar you are buying.

How often should I check a puppy’s collar?

Often. Battersea says puppies can outgrow a collar very quickly. A quick two-finger check each time you put the leash on catches it early.

Why does my dog keep slipping out of their collar?

Their head may not be much wider than their neck. Whole Dog Journal says this is common in sighthounds such as Greyhounds and in thick necked breeds such as Pugs, and suggests a limited slip (martingale) collar for them.

Should a dog wear a collar all the time?

Best Friends says your dog should always have a current ID tag on the collar. If a collar stays on during unsupervised time or play with other dogs, Whole Dog Journal suggests a quick release or breakaway style, and says martingale collars should come off when your dog is left alone or playing.

Ready to choose one? See our best dog collars guide, how to measure a dog for a harness if your dog pulls, and the dog leash, harness and carrier buying guide.