Dog Collar Size Chart 2026: How to Measure Your Dog's Neck (and Why One Brand's Medium Is Another's Large)

Quick Answer: To find your dog’s collar size, wrap a soft tape measure around the neck where the collar will sit, snug but not tight. Then pick the size whose adjustable range puts that number near the middle, and check that you can slide two fingers under the buckled collar. As a rough guide, PetSmart’s size chart puts toy breeds at 8 to 12 inches, small dogs like Pugs at 10 to 14 inches, Beagles and Border Collies at 14 to 20 inches, Labs and Golden Retrievers at 16 to 26 inches and giant breeds at 24 to 30 inches. Always use the brand’s own chart, because size labels aren’t standard: a 19-inch neck fits a Medium in GoTags’ quick-release collars (14–20 in) but needs a Large at Orvis (17–20 in) and in GoTags’ own metal-buckle line (18–21 in).

Dog collar sizes, by the numbers

• 4 brands, 4 places to put the tape. The AKC says to measure “around the base of your dog’s neck where the collar sits.” Orvis says the opposite: measure the middle of the neck and “don’t measure at the base.” GoTags says to measure the center, “a few inches down from their head,” and Auburn Leathercrafters says to measure “at the narrowest point.” What they all agree on is measuring where the collar will actually rest.
• 13 to 20 inches: the span that “Medium” covers across brands. Orvis’s Medium fits 13–17 in, GoTags’ metal-buckle Medium 16–18.25 in, and PetSmart’s and GoTags’ quick-release Medium both 14–20 in, per each brand’s chart on November 6, 2026.
• 2 fingers: the fit check given by the AKC, PetSmart, Orvis, Pawtitas, Auburn and Halo. You should be able to slide two fingers under the collar once it’s buckled.
• 10 times: in a study of eight dogs, the neck pressure from all three 20 mm collars tested was roughly ten times the 0.43 N/cm² capillary-pressure estimate the authors cite for skin damage (Hunter, Blake and Ferro de Godoy, Veterinary and Animal Science, 2019). A collar that’s too tight adds to that.
• 90%: share of lost dogs that were wearing a collar in an ASPCA-funded survey (Weiss, Slater and Lord, Animals, 2012). The collar is what carries your dog’s ID home, so it has to stay on.

We compiled this guide from the size charts and fit instructions that collar makers publish on their own stores, PetSmart’s sizing chart and the AKC’s measuring guide, all checked on November 6, 2026. We don’t test collars ourselves. Prices are the makers’ own, and they change often.

Dog collar size chart by neck size and breed

This is PetSmart’s dog collar chart, which lines up with the size labels most US collar brands use. Treat the breeds as a starting point and measure your own dog: neck sizes vary a lot within a breed, and adjacent sizes overlap.

Source: PetSmart’s sizing charts page, November 6, 2026. PetSmart lists a single weight for the XXS, M and L sizes rather than a range, and labels the width column “leash width”.

How to measure your dog’s neck for a collar

1. Use a soft tape measure. A sewing tape works best. If you don’t have one, the AKC suggests a piece of string, ribbon or a shoelace: wrap it around, mark where it overlaps, then lay it flat against a ruler.
2. Have your dog stand. The AKC says a standing dog gives the most accurate measurement for collars, harnesses and coats. A sitting or lying dog bunches the skin at the neck.
3. Measure where the collar will sit. On most dogs that’s partway down the neck, not right behind the ears. Orvis warns against measuring at the base of the neck or just behind the ears, because the collar won’t sit there. The AKC’s advice to measure “at the base, where the collar sits” means the same spot on most dogs. For long-necked breeds like Greyhounds and Whippets, whose collars ride high, the AKC says to still measure lower on the neck, between the withers and where a standard collar would rest.
4. Keep the tape snug, not tight. Read the number with the tape lying flat against the coat. Long or thick coats add to the measurement, so press the tape through the fur to the neck.
5. Or measure the collar that already fits. If your dog’s current buckle collar fits well, measure it instead. Auburn Leathercrafters says to measure from the buckle’s center bar, where it joins the collar, to the hole you’re using.
6. Match the number to the brand’s chart. GoTags puts it plainly: “Your dog’s measured neck size must fit within the collar’s adjustable neck size range.”

Don’t add extra inches to the measurement for a flat adjustable collar. The two-finger room comes from how you buckle the collar, not from buying a bigger size. The exceptions are slip collars and buckle-less martingales, which have to fit over the head (see below), and fixed-length leather collars, where the labeled length means different things at different makers.

Brand size charts compared: same neck, different label

Every brand below sizes by neck measurement, but each one draws the lines between sizes in different places. These are each brand’s own published ranges, checked on November 6, 2026.

Here is what that means for three real neck sizes:

The lesson: never buy by letter, and never assume your dog’s size at one brand carries over to another. The AKC makes the same point, warning that sizing may not carry over between brands or even between styles from the same brand. GoTags is the clearest example: a 17-inch neck is a Medium in both of its lines, but a 19-inch neck fits the quick-release Medium and needs the metal-buckle Large.

How tight should a dog collar be? The two-finger rule

Once the collar is buckled, you should be able to slide two fingers flat between the collar and your dog’s neck. Six of the sources in this guide (the AKC, PetSmart, Orvis, Pawtitas, Auburn and Halo) give that same rule.

• Too tight: you can’t get two fingers under it, or the collar leaves a dent in the fur when you take it off. A tight collar presses on the neck all day. With the leash at a light, steady tension, the Hunter 2019 study measured roughly ten times the authors’ capillary-pressure estimate under each of three ordinary 20 mm collars, and a tight fit only adds to the baseline.
• Too loose: the collar slides up over your dog’s ears when you pull it gently toward the head. A dog can back out of a collar like that on a walk, and a loose collar can catch on a crate wire or a fence.
• Check again after a bath or a haircut. A thick coat clipped short or a wet coat changes the fit. So does weight gain or loss.

Pressure isn’t only a comfort issue. Pauli and colleagues found that pressure on the neck from a collar raised the pressure inside the eye in a study of 26 dogs (51 eyes), while the same force through a harness did not (Journal of the American Animal Hospital Association, 2006). The authors advise a harness for dogs with glaucoma or thin corneas. If your dog pulls on the leash, the fit of the collar matters less than switching the leash to a no-pull harness.

Collar width: how wide should your dog’s collar be?

Width scales with the size of the dog: narrow webbing for toy breeds, wider webbing for big dogs. The brands in this guide pair width and neck size like this:

Width matters for the things you hang on the collar too. GoTags sizes its silent slide-on tags and AirTag holders by collar width (3/8 in, 5/8 in, and 3/4 to 1 in), so order the holder to match the collar, not the dog. And if you plan to clip on a GPS tracker, Tractive says the rubber clip that comes with the DOG 6 fits collars up to 2.8 cm, about 1.1 inches wide. A 1.5-inch giant-breed collar is too wide for it.

Leather collars: what the length on the label means

Fixed-hole leather collars are sold by length, and the makers don’t agree on what that length measures.

• Mendota sizes its leather collars to the middle of the five holes, so “each collar is adjustable 2 inches up or down from its indicated size.” Its 18-inch collar fits necks from 16 to 20 inches. The Leather Standard collar in chestnut costs $33.49 (narrow) or $40.49 (wide).
• Auburn Leathercrafters labels by the longest fit. On its Rolled Collar ($50 and up) size guide, a 20-inch collar fits necks from 16 to 20 inches and a 22-inch collar fits 18 to 22 inches.

So an “18-inch” Mendota collar fits a 20-inch neck, but an 18-inch Auburn collar doesn’t. Read the size guide on the exact product page before you order, especially for personalized leather: Auburn makes you confirm that you’ve measured your dog and read the size guide, and customized collars are nonreturnable. Our leather dog collar guide compares both makers in detail.

Martingale and slip collars: measure the head too

A martingale tightens a limited amount when the dog pulls, so it can’t slip over the head the way a loose flat collar can. That changes how you size it.

• Buckle-less martingales and slip collars go on over the head, so they have to open wide enough to pass the widest part of the head and still close to a snug fit on the neck. Measure both. Mendota says to size its slip collars up “at least 2 sizes” from the neck measurement so the collar fits over the head. Mendota’s slip collars come in 2-inch steps, so that’s at least 4 inches longer than the neck.
• Buckle martingales like Ruffwear’s Web Reaction ($29.99, five sizes from 11–14 in to 23–26 in) open at a buckle, so they only need the neck size.
• Lupine’s limits: Lupine makes its martingales only in 3/4-inch (10–14 and 14–20 in, $14.65) and 1-inch widths (15–22 and 19–27 in, $19.55). It says they are for training and leash walking, shouldn’t be left on an unattended or unleashed dog, and that it doesn’t make martingales for puppies or small dogs.

Our martingale collar guide compares seven martingales, buckle and slip-on, and shows how to check the fit with the control loop pulled tight. If your dog keeps backing out of collars, compare martingales with a proper escape-proof harness in our escape-proof dog harness guide.

Puppies, personalized collars and GPS collars

Puppies. A growing puppy can outgrow a collar fast, so buy a cheap adjustable one and recheck the two-finger fit every week or so. Lupine’s smallest 1/2-inch collar fits 6–9 inch necks for $9.10. Don’t buy a personalized collar for a puppy: GoTags says its personalized collars can’t be returned or resized if you order the wrong size, and Pawtitas and Auburn also treat personalized items as nonreturnable. Fi offers a free swap of its Series 3+ collar once a puppy is fully grown, which it calls the Fi Puppy Warranty.

Personalized collars. Embroidered or engraved text can disappear when you take a collar in. Orvis warns that on its Small and Medium sizes, “personalization may be partially obscured when the collar is adjusted to a smaller size.” If your dog sits near the bottom of a size range, choose the smaller size or a personalized collar with a nameplate.

GPS and smart collars. Tracker collars size differently from regular collars:

For full reviews, see our best GPS collar for dogs guide, our Halo Collar 5 review and our Tractive review.

Cats. Cat collars are a different product: they should be breakaway collars that release under load, and most cover a neck range of about 7 to 13 inches. See our breakaway cat collar guide.

Common sizing mistakes

1. Buying by letter. “Medium” covers anything from 13 to 20 inches depending on the brand. Use the inches.
2. Buying by weight. Weight charts are rough. A deep-chested Whippet and a stocky French Bulldog can weigh the same and need very different collars.
3. Landing at the very end of a range. If your dog measures 16 inches and a collar fits 11–16 in, it’s already at its loosest setting with no room for a winter coat. Choose the size where you land in the middle.
4. Adding inches to a flat collar. The two-finger room comes from how you buckle it. Only slip collars and buckle-less martingales need extra length, to clear the head.
5. Never rechecking. Puppies grow, adult dogs gain and lose weight, and coats change with the seasons. Check the fit whenever you check the ID tag.
6. Forgetting what clips on. A tag holder, AirTag case or GPS clip has to match the collar’s width. Check the pet ID tag or tracker’s width limit before you pick a collar.

The Bottom Line

Measure your dog’s neck with a soft tape where the collar will sit, with your dog standing, then look up that number on the chart for the exact collar you want and pick the size that puts it in the middle of the range. Buckle it so two fingers slide underneath. Use PetSmart’s chart (XS 8–12 in, S 10–14 in, M 14–20 in, L 16–26 in, XL 24–30 in) only as a starting point, because brands draw the size lines in different places. A 19-inch neck fits a Medium in GoTags’ quick-release line but needs a Large at Orvis. For leather, check whether the labeled length is the middle hole (Mendota) or the longest fit (Auburn). For martingales and slip collars, measure the head as well. Once the collar fits, make sure it carries your phone number, and if your dog is a bolter, pair it with a GPS dog tracker. For nighttime walks, add a light-up collar alongside the one that holds the leash.

Sources (checked November 6, 2026): PetSmart sizing charts; AKC “How to Measure Your Dog for Clothes and Gear” (Courtney Campbell, updated August 10, 2026); size charts and product pages from GoTags, Orvis, Ruffwear, Lupine Pet, Pawtitas, Mendota Products and Auburn Leathercrafters; Halo Collar, Fi and Tractive product pages; Hunter, Blake and Ferro de Godoy, Veterinary and Animal Science (2019); Pauli et al., Journal of the American Animal Hospital Association (2006); Weiss, Slater and Lord, Animals (2012).