How to choose the right harness size for your dog?

To choose the right harness size, measure your dog's chest girth just behind the front legs, as well as its neck girth, then compare both measurements to the size chart of the chosen model rather than relying on weight alone, since body shape varies a lot between breeds.

1. Why harness size matters as much as the model

A harness with the right shape but the wrong size loses most of its point: too loose, it slides and gives the dog a chance to slip out while pulling or backing up; too tight, it chafes, restricts breathing and can mark the coat. The right size is therefore the first condition for a harness to stay comfortable and safe over time.

2. How to take the measurements correctly

Ideally, take these measurements with two people: one holds the dog calmly with a treat, the other wraps the tape around it. A dog that keeps moving will give an unreliable reading, when the whole point is to get a figure accurate to the centimetre. Two measurements are enough in most cases:

• Chest girth: using a soft tape measure, wrap it around the dog's chest just behind the front elbows, at the widest point of the rib cage. This is the most important measurement for a harness.
• Neck girth: measure the base of the neck, where a collar would sit, useful especially for adjustable-neck or vest-style harnesses.
• Weight: only a rough guide, since two dogs of the same weight can have very different builds (a stocky, muscular dog does not have the same chest girth as a slim, lanky dog of the same weight).

Take these measurements with the dog standing, without pulling the tape too tight, leaving the equivalent of two fingers of ease. If you do not have a soft tape measure handy, a piece of string wrapped around the dog and then measured against a ruler works just as well.

3. Size chart, as a general guide

Sizes vary from one manufacturer to another: this table gives a general order of magnitude, but the size chart shown on the product page of the chosen model remains the reference to follow.

Size	Approximate chest girth	Example profiles
XS / S	25 to 45 cm	Chihuahua, Yorkshire Terrier, adult cat, small puppy
M	45 to 60 cm	French Bulldog, Cocker Spaniel, Border Collie
L	60 to 75 cm	Labrador, Australian Shepherd, Husky
XL	75 cm and above	German Shepherd, Rottweiler, large guard dog

4. Checking the fit once the harness is on

Once the harness is on, a few simple checks confirm the size is right:

• You should be able to slide two flat fingers between the straps and the dog's body, both on the chest and on the back.
• The harness should not slide forward or sideways when you gently pull on the leash.
• The front legs should move freely, with no strap rubbing under the armpits.
• Watch your dog for the first few minutes: if it scratches, rolls on the ground or refuses to move, recheck the fit before concluding it simply dislikes the harness.
• Recheck the fit after a few outings: nylon straps can loosen very slightly during the first few days, especially on a brand-new harness.

5. Special cases depending on body shape

Some body shapes need extra attention:

• Puppies grow fast: choose a model adjustable at several points and recheck the size every few weeks rather than buying a final harness too early.
• Deep-chested, slim-necked breeds (whippets, greyhounds) often need a harness with a lower, well-fitted chest strap to avoid slipping.
• Stocky, muscular breeds (bulldogs, pugs) sometimes have a neck girth almost as wide as the chest girth: check both measurements before ordering.
• A dog between two sizes on the manufacturer's chart: it is generally better to choose the larger size, then tighten the straps using the adjustment points, rather than the other way round.

6. Why it pays to measure rather than guess

Buying a harness based only on the breed, or on a similar-looking dog's harness seen on a walk, remains risky: within the same breed, weight and build vary noticeably from one dog to another, even more so for mixed breeds. The few minutes needed to take measurements save a lot of back-and-forth with a harness that is too big or too small, especially when ordering online without being able to try it first. Write down both measurements somewhere: they will come in handy for quickly comparing several models without reaching for the tape every time.

7. Our adjustable harnesses, available in several sizes

For a small dog, an adjustable fur-lined harness or a vest-style harness adjusts easily across several notches. For a medium to large dog, a classic adjustable harness offers several adjustment points at the chest and back. Browse all the models, in every size, in the dog harnesses collection.

Still pulling even with the right size harness? Read our article my dog pulls on the leash, which harness should I choose to fine-tune the most suitable attachment type.