Harness sizing trips up a lot of owners — breed names only get you so far, because dogs within a breed vary. This UK guide gives you a breed-by-breed starting point, then shows you how to confirm with a quick measurement so you order the right size first time. For choosing the right type of harness, see our no-pull harness guide.
How do I measure my dog for a harness?
You need one key number — the chest (girth):
- With your dog standing, wrap a soft tape around the widest part of the chest, just behind the front legs.
- Keep it snug but not tight — you should fit two fingers under the tape.
- Note the measurement in centimetres. Also measure the base of the neck for harnesses with a neck strap.
The chest measurement always beats the breed guess. If you only do one thing, do this.
Dog harness size chart by breed
Use this as a starting point, then confirm with your dog's actual chest girth:
| Size | Chest girth | Example breeds |
|---|---|---|
| XS | 33–43 cm | Chihuahua, Yorkshire Terrier, Toy Poodle, Maltese, young puppies |
| S | 42–54 cm | Miniature Dachshund, Pug, Shih Tzu, Jack Russell, Pomeranian |
| M | 53–66 cm | Cocker Spaniel, Border Collie, French Bulldog, Beagle, Mini Schnauzer |
| L | 65–80 cm | Labrador, Golden Retriever, Boxer, German Shepherd, Staffie |
| XL | 78–96 cm | Rottweiler, Mastiff, Great Dane, Bernese, larger crossbreeds |
Ranges overlap on purpose — that is where measuring decides it.
What if my dog is a crossbreed or between sizes?
Measure the chest and pick the size whose range your number sits in. If you land right on the boundary between two sizes, size up — a harness can be tightened with its adjusters, but one that is too small will rub and restrict movement. Crossbreeds should always be measured rather than guessed from the breeds in the mix.
Puppy harness sizing
Puppies grow fast, so expect to size up at least once. Choose an adjustable harness, re-measure every couple of weeks, and check the fit often. For everything else a new pup needs, see our new puppy checklist and puppy edit.
How tight should a harness be?
Use the two-finger rule: you should be able to slide two fingers flat under any strap. Tighter and it may rub; looser and your dog could wriggle free or the harness could twist. Check the straps sit clear of the front legs, and that there is no gaping at the chest when the lead is taut.
Frequently asked questions
How do I measure my dog's chest for a harness?
Wrap a soft tape around the widest part of the chest, just behind the front legs, snug enough to fit two fingers underneath. Measure in centimetres and match it to the size chart.
My dog is between two harness sizes — which do I choose?
Size up. The adjusters let you tighten a slightly larger harness, but a too-small one will rub and limit movement.
Can I size a harness by breed alone?
Breed is only a starting point because dogs within a breed vary a lot. Always confirm with your dog's chest measurement before ordering.
What size harness does a Labrador need?
Most adult Labradors take a size L (chest roughly 65–80 cm), but measure to be sure — lean or larger Labs can sit at the edges of that range.
Measured up? Shop our dog harnesses and matching leads. Free UK delivery on every order, with 14-day easy returns if the size isn't quite right.
Related guides
- How to Choose a No-Pull Dog Harness: UK Size & Safety Guide
- New Puppy Checklist: Everything You Need for the First Week
- Dog Bed Buying Guide: How to Choose the Right Bed
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