· Nora Whitfield
How to measure a dog for a harness
Returns in this category are overwhelmingly about fit, and fit problems are overwhelmingly about measuring by weight. Two dogs of 20 kg can be shaped entirely differently, and only one of them fits the harness.
The measurement that decides the size
Chest girth. Stand your dog squarely. Pass a soft tape around the deepest part of the ribcage, just behind the front legs, and bring it back to where you started. Keep it snug against the body without compressing.
Three details that change the number:
Press through the coat. On anything fluffier than a Labrador you are measuring fur unless you push the tape down to the body. On a Pomeranian or a Chow this can be four or five centimetres of difference — a whole size.
Measure three times. Dogs move, tapes slip backward onto the narrower part of the ribcage, and a slipped tape always reads small. Take the largest of the three.
Behind the legs, not at the shoulder. The widest point is a hand's width behind the elbow. Measuring at the shoulder gives a number that is too small and a harness that rides up.
The second measurement people forget
Neck girth, taken low — where a harness sits, at the base of the neck, not up where a collar sits. Harnesses with a closed neck opening have to pass over the head and then sit on this measurement.
This is where barrel-chested and thick-necked breeds get caught. French bulldogs, pugs, staffies and boxers routinely pass on chest and fail on neck. When the two measurements point to different sizes, go by the tighter one and take up the difference with the adjusters.
Why the weight column is the least useful one
Every harness chart publishes a weight range because buyers know their dog's weight and not its chest. It is a convenience, not a specification.
A 20 kg whippet and a 20 kg French bulldog are not remotely the same shape. Charts are written to accommodate both, which means they are written loose — and that is exactly what we found when we checked them.
Buyer reports — we read every review of our front-clip harness that named both a size and a real measurement. Two independent buyers fitted 35 kg Labradors into size L — the chart caps L at 30 kg — and both reported adjustment left over. A 25 kg pitbull also fitted L. At the other end, a buyer with a 38 kg dog found XL loose, and one US buyer recommended sizing down because the back panel ran long for the stated weight. (verified buyer reviews, read September 2026)
That is a consistent enough pattern to act on: when you are between two sizes, take the smaller one. It is the opposite of the usual advice, and it comes from the reports rather than the chart.
Reading the chart you are given
| Column | How much to trust it |
|---|---|
| Chest girth | The one that decides. Measure it properly and follow it. |
| Neck girth | Decides for thick-necked and flat-faced breeds. Do not skip it. |
| Weight | Sanity check only. If it contradicts the chest measurement, the chest wins. |
| Breed examples | Marketing. Two Labradors can be 12 kg apart. |
A tolerance is usually stated alongside: flat-measured figures with an error of 1–2 cm, and a recommendation to take the larger size in an overlap. Our buyer data points the other way on this product, and that is the advice we give.
The sizes we carry
| Size | Front-clip harness | Personalised vest |
|---|---|---|
| XS | — | 39–47 cm chest · 30–38 cm neck |
| S | 43–56 cm | 45–58 cm · 36–47 cm |
| M | 56–69 cm | 51–67 cm · 47–64 cm |
| L | 69–81 cm | 66–90 cm · 50–68 cm |
| XL | 81–107 cm | 71–97 cm · 56–77 cm |
| XXL | — | 75–101 cm · 61–85 cm |
The vest reaches further at both ends; the front-clip harness is the one with the chest attachment. Which matters more depends entirely on whether your dog pulls — the trade-off is set out on the front clip versus back clip page.
Growing dogs
Measure monthly. Buy for the current measurement: a harness sized for the dog your puppy will become is loose on the dog you have, and loose is how dogs back out near roads. The puppy harness page covers when to size up and when to accept you will buy twice.
After it arrives
Measuring gets you the right size; fitting gets you the right harness. The chest panel has to sit low on the breastbone, and two flat fingers should slide under every strap. Re-check after a week once the webbing has settled. Full walkthrough in how to put a harness on a dog.
Sizing help by dog: small dogs, big dogs, puppies. Our method is on how we test.
Nora Whitfield · Leash-training specialist, Heelbrook
Nora has spent twelve years walking dogs that pull — first as a shelter volunteer, now fitting harnesses full time. She has fitted and stress-tested more than 400 harnesses across every body shape, and she still walks two ex-shelter pullers of her own.