How to Measure a Dog for a Coat or Jumper

Most dog coats that get returned were not the wrong product, they were the wrong number. And most sizing charts are ordered in a way that makes people pick the wrong one — by back length, when the measurement that actually decides whether a coat fits is the chest.

The three measurements

Do this with your dog standing up, not sitting or lying, and use a soft tailor's tape. A piece of string marked with your thumb and then held against a ruler works perfectly well.

1. Back length. From the base of the neck — where a collar sits, between the shoulder blades — straight along the spine to the base of the tail. Not to the tip of the tail.

2. Chest girth. All the way around the deepest part of the chest, just behind the front legs. Snug, not tight — you should be able to slip two fingers under the tape.

3. Neck. Around the neck where the collar sits, again with two fingers of room.

Which one decides the size

Chest girth. A coat that is slightly too long looks a bit odd. A coat that is too tight around the chest restricts the shoulders, and the dog will refuse to walk in it — usually by planting themselves and staring at you.

Back length only determines coverage. If it is a little short, the coat sits above the tail, which is fine. If it is a little long, it can catch when they squat, which matters more for females and is worth checking on a raincoat.

If your dog is between sizes

Go up. Always. A slightly roomy coat is a minor irritation; a tight one does not get worn.

Two exceptions where you should think harder rather than just sizing up:

- Deep-chested, narrow-waisted breeds — greyhounds, whippets, lurchers, salukis. Their chest girth suggests a much bigger size than their back length does. Look for breed-specific cuts, or a coat with an adjustable waist strap. - Long-and-low breeds — dachshunds, corgis, bassets. The opposite problem: a coat long enough for the back is far too big around. Again, look for a cut made for the shape.

For both, the breed or shape-specific fit matters more than the size letter.

Knitted jumpers run smaller than coats

Knitwear has less give across the chest than a fleece or a padded coat, and it does not adjust. If you are buying a Christmas jumper or any knitted layer, size up more readily than you would for a raincoat, and check behind the front legs once it is on — rubbing there is the single most common reason a dog refuses to walk in a jumper, and they cannot tell you. They just stop.

Checking the fit once it arrives

- Two fingers should slide under the neck and chest openings. - The front legs should move freely — walk them a few steps indoors before removing tags. - Nothing should press on the throat. - Check the harness opening lines up if you use one, or buy a coat with a harness hole. - Watch them for a minute. A dog who freezes, walks strangely, or tries to reverse out of it is telling you it does not fit.

A note on which dogs need one at all

Sizing is academic if the coat is unnecessary. Thin-coated and short-haired breeds, older dogs and puppies genuinely benefit below about 7°C. Double-coated breeds — huskies, German shepherds, collies — are already wearing one, and adding another risks overheating. There is a breed-by-breed guide here.

Inches or centimetres?

Most UK makers list both; some list only one. Measure once in centimetres and convert if you need to — 1 inch = 2.54cm — rather than measuring twice.

Where this catches people out is buying from a US or EU brand, where the same size letter covers a different range. Never buy on the letter. Always find the actual cm or inch range in that specific brand's chart, because an "M" from two makers can differ by 10cm of back length.

Measuring without a tape measure

Perfectly doable, and more accurate than guessing:

1. Take a length of string, a phone charger cable, or a bootlace, and run it along the measurement. 2. Mark the point with your thumb, or a knot, or a bit of tape. 3. Hold it against a ruler, a tape measure from a toolbox, or a piece of A4 paper — the long edge is 29.7cm, the short edge 21cm, which is enough to measure most dogs in two steps.

A soft dressmaking tape is easier if you have one, and they cost almost nothing. A rigid metal builder's tape does not follow the curve of the chest and will read short.

Measuring a wriggler

- Do it when they are tired, after a walk, not before one. - Have someone else hold a treat at nose height so the dog stands square. - Measure over the coat they will wear it on, not against wet or freshly-groomed fur. - If they will not stand still, measure a jumper that already fits while it is laid flat, and double the chest measurement.

Dog height, and when it matters

Height at the withers — the ridge between the shoulder blades — is measured from the floor with the dog standing square. It matters for crates, carriers, car barriers and stair gates. It is not used for coat sizing, which is why almost no coat chart asks for it, and it is a common reason people arrive with the wrong three numbers.

Size charts by breed: useful shortcut, unreliable rule

Breed-based charts ("Labrador = L") are a starting point, not an answer. Within any breed there is a wide spread — a working cocker and a show cocker are different shapes, and a rescue of unknown parentage fits no chart at all.

Use a breed chart to narrow it to two sizes, then measure to pick between them. And for deep-chested or long-and-low breeds, skip the chart and go by chest girth, because that is exactly where the breed averages break down.