How to Measure Your Dog for a Harness | Best Pet Supplies Guide

To size a dog harness, you need two measurements: the neck and the chest girth. Compare both to the size chart for the exact harness you plan to buy. The Rabbitgoo size and wear guide says not to select a size from weight alone, because dogs of the same weight can be built very differently.

This guide walks through each step, shows an example size chart, and explains how to check the fit once the harness is on. When you are ready to compare styles, the Collars, Harnesses & Leashes category is a good place to start.

What You Need

A soft tape measure, the cloth or sewing kind. A metal construction tape does not wrap around a dog comfortably.
Treats to keep your dog standing still and relaxed.
A pen and paper or a phone note, so you can write each number down right away.
A helper, if your dog wiggles. This is optional but makes it easier.

Have your dog stand on all four feet on a flat floor. If you do not own a soft tape, wrap a piece of string around the dog, mark it, then lay it flat against a ruler.

Step 1: Measure the Neck

Measure around the base of the neck, close to where the neck meets the shoulders, according to the American Kennel Club. This is lower than most people expect.

The same Rabbitgoo guide makes the point that you should measure low, where the harness will actually sit, and not at the spot where the collar rests. Keep the tape snug but not tight, and write the number down.

Step 2: Measure the Chest Girth

Chest girth is the distance around the widest part of the ribcage, measured while your dog is standing. The AKC guide describes it this way, and the Rabbitgoo guide places it just behind the front legs.

Wrap the tape fully around the body, behind the front legs and over the widest point of the ribs. Check that the tape sits level on both sides and does not twist or sag under the belly. Write down this number too.

Measurement	Where to place the tape	Dog position
Neck	Base of the neck near the shoulders, where the harness sits (not the collar spot)	Standing
Chest girth	Widest part of the ribcage, just behind the front legs	Standing

Step 3: Compare to the Brand’s Chart

Now match your numbers to the size chart for the specific harness you are considering. As an example, Ruffwear’s Front Range fit guide lists these girth ranges in inches:

Size	Girth range (inches)
XXS	13 to 17
XS	17 to 22
S	22 to 27
M	27 to 32
L/XL	32 to 42

This chart is an example only. Every brand and every harness style has its own chart, so always use the one for the product you are buying. Also check whether that chart asks for chest girth, neck, or both.

Notice that the ranges touch at the edges. A dog with a 22-inch girth falls on the line between XS and S, which brings us to the between-sizes question below.

The Two-Finger Fit Check

The measuring tape and the finished harness both follow the same rule of thumb: leave room for about two fingers. The AKC guide suggests keeping two fingers under the tape when you measure. The Rabbitgoo guide says that once the harness is on, you should be able to slide two fingers under each strap.

Here is a simple routine:

Put the harness on your standing dog and adjust the straps.
Slide two flat fingers under each strap. It should be snug, with no big gaps and no pinching.
Walk your dog around for a few minutes and let them turn in circles.
Check again. Rabbitgoo recommends rechecking after the dog walks and turns, because straps can shift once your dog is moving.

Between Sizes?

If your dog’s numbers land between two sizes, the AKC guide suggests choosing an adjustable style or the larger size. Ruffwear’s guide likewise says to go up a size when your dog is between sizes.

Sizing up only works if the straps can be tightened properly. After you adjust the harness, run the two-finger check again. If the harness still shifts or leaves big gaps, check the brand’s chart again or look at a different style rather than just cinching the straps harder.

Puppies and growing dogs change quickly, so measure again before you buy a replacement.

Signs of a Poor Fit

A harness that is too loose can let a dog slip out of it, according to VCA Animal Hospitals. VCA also advises that a harness should not rub behind the front legs, and that dogs should not wear gear when unsupervised.

Watch for these signs:

The harness twists to one side or rides up toward the neck while your dog walks.
Your dog can back out of it or wriggle a shoulder free.
Straps rub behind the front legs.
You cannot get two fingers under a strap, or you can fit a whole hand.
Your dog seems reluctant to move, or you see red or irritated skin after a walk.

If your dog pulls hard on walks, our roundup of no-pull dog harnesses compares front-clip designs and their size charts.

If your dog shows any discomfort or skin irritation, stop using the harness and talk to your veterinarian. You can read more about how we research gear on our How We Research page.

Frequently Asked Questions

Can I choose a harness size by my dog’s weight?

Weight alone is not a reliable guide. The Rabbitgoo guide says not to select a size from weight alone, so measure your dog’s neck and chest girth and compare them to the brand’s chart.

Where exactly do I measure my dog’s neck for a harness?

Measure low at the base of the neck, near the shoulders, where the harness will sit. This is lower than the spot where a collar rests.

How tight should a dog harness be?

Snug enough that it does not shift, but loose enough that you can slide two fingers under each strap. Check again after your dog has walked and turned around.

What if my dog is between two harness sizes?

The AKC suggests an adjustable harness or the larger size, and Ruffwear’s guide also says to size up. After sizing up, tighten the straps and repeat the two-finger check.

Should I measure my puppy again before buying a new harness?

Yes. Puppies grow quickly, so take fresh neck and chest measurements right before you order, and compare them to the chart for that exact harness.

Sources

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Best Pet Supplies Guide

Best Pet Supplies Guide publishes research-based buying guides, size guides and care how-tos for dog, cat and pet home supplies, using manufacturer specifications and guidance from reputable pet-care organizations.