Dog Harness Size Calculator
What Size Harness Does My Dog Need?
Enter your dog's chest measurement and we will match it to the real size charts of the harnesses we sell, with live stock for that exact size.
A harness that fits well is comfortable on walks and holds your dog properly in the car. One that is too loose lets a dog wriggle free, and one that is too tight rubs under the legs. This free dog harness size calculator checks your dog's chest and neck against the size charts of the harnesses in our range and shows the size to order, with stock for that size.
How to Measure Your Dog for a Harness
With your dog standing, wrap a soft tape around the widest part of the ribcage, just behind the front legs. Keep it snug, not tight.
Measure around the base of the neck where a collar would sit. This checks the neck straps will close.
Weigh your dog as a cross check. Chest size always comes first, as two dogs of the same weight can be very different shapes.
No soft tape? Wrap a piece of string around your dog, mark it, then lay it flat against a ruler.
Dog Harness Size Chart
This is the size chart for our car harness and seat belt set, which covers the widest range of sizes we stock.
| Size | Chest girth | Neck girth | Often fits |
|---|---|---|---|
| XXXS | 28 to 33cm (11 to 13in) | 22 to 27cm | Tiny puppies, small Chihuahuas |
| XXS | 33.5 to 41cm (13.5 to 16in) | 27.5 to 30cm | Chihuahua, Yorkshire Terrier |
| XS | 41.5 to 46cm (16.5 to 18in) | 30.5 to 36cm | Miniature Dachshund, Shih Tzu |
| S | 46.5 to 53cm (18.5 to 21in) | 36.5 to 43cm | Cavapoo, Jack Russell, Pug |
| M | 53.5 to 68cm (21.5 to 27in) | 43.5 to 64cm | Cocker Spaniel, French Bulldog, Beagle |
| L | 68.5 to 94cm (27.5 to 37in) | 64.5 to 78cm | Labrador, Golden Retriever |
Other harnesses use different charts, so the calculator checks each one on its own. You can see every harness in our dog car harness range.
Harness Size by Breed
| Breed | Typical adult chest | Likely size |
|---|---|---|
| Chihuahua | 30 to 40cm | XXS |
| Miniature Dachshund | 36 to 46cm | XXS to XS |
| Cavapoo | 40 to 55cm | XS to S |
| French Bulldog | 50 to 66cm | S to M |
| Cocker Spaniel | 55 to 68cm | M |
| Staffordshire Bull Terrier | 60 to 75cm | M to L |
| Labrador | 70 to 86cm | L |
These are rough ranges. A deep chested Spaniel and a slim one can sit a full size apart, so measure if you can. For car seats by breed, see our size chart by breed.
The Two Finger Fit Check
- You can slide two flat fingers under every strap, but not your whole hand.
- The chest strap sits about a hand width behind the front legs, not in the armpit.
- The harness does not twist or slide to one side when your dog moves.
- Your dog cannot back out when you gently pull the lead forwards.
- Your dog walks, sits and lies down normally while wearing it.
Car Harness or Walking Harness?
Car harness
Made to clip to a seat belt tether so your dog stays in place. Look for strong fittings, a back clip and straps that wrap the body, not just the neck. Pair it with a dog seat belt.
Walking harness
Made for comfort on the lead, often with padding, a handle and reflective strips. Many can also clip to a car tether, but check the clip is on the back.
Whatever you choose, the tether should clip to the harness, never to a collar. Read why in our guide are dog seat belts safe.
Between Sizes, Puppies and Thick Coats
Between two sizes: most harness makers say choose the larger size and tighten the straps. A harness with spare adjustment fits better than one at its very limit.
Puppies: measure every two weeks during growth spurts. Choose a size with room to let the straps out, and expect to size up at least once.
Thick or long coats: press the tape down gently through the coat so you measure the dog, not the fluff. Check the fit again after a groom.
Does a Harness Meet UK Rules for Dogs in Cars?
Highway Code Rule 57 says dogs should be suitably restrained so they cannot distract you or be hurt if you stop quickly. A seat belt harness is one of the methods it lists. Our UK law guide explains more.
Fit matters more than price. A loose harness can slip off in a sudden stop. Check the fit before every long trip. Our harnesses, seats and tethers are for comfort and containment and are not crash tested. If your dog rides in a car seat, use our car seat size calculator too.
Harness Sizing Questions
What size harness does a 10kg dog need?
Usually S or M, but weight alone is not enough. A 10kg Jack Russell and a 10kg Cavapoo can need different sizes, so measure the chest.
Should a dog harness be tight or loose?
Snug. Two flat fingers should fit under each strap. Any looser and your dog may slip out.
Is chest or neck size more important?
Chest. It decides the size. The neck measurement just checks the neck straps will close comfortably.
Can I use my walking harness in the car?
Often yes, if it has a strong back clip for the tether. Avoid clipping a tether to a front no pull ring.
Frequently Asked Questions
1. How do I choose the right size dog car seat?
Check your dog’s weight and body length. The ideal seat should allow your pet to sit and lie down comfortably without feeling loose or unstable.
2. Are your dog car seats suitable for UK vehicles?
Yes, our seats are designed with UK cars in mind and include secure attachment systems such as headrest straps and seatbelt connections.
3. Can my dog stay safely restrained during sudden braking?
Our car seats help keep dogs positioned securely, reducing movement during sharp turns or sudden stops for safer journeys.
4. Do your dog car seats work for small breeds?
Absolutely. We offer small dog car seats and booster seats specially designed for smaller breeds to travel comfortably and safely.
5. What about large dogs — do you have bigger sizes?
Yes, we provide large dog car seats with extra space and support so bigger breeds can travel securely without feeling restricted.
6. How do I keep my dog car seat clean?
Most of our seats are made from durable, stain-resistant fabrics, and many include removable, machine-washable covers for easy cleaning.
7. Do I also need a dog car seat cover or hammock?
Many owners pair their seat with a dog car seat cover or hammock for extra protection against fur, mud, and wet paws.
8. Are the materials waterproof and scratch-resistant?
Yes, our products use premium materials designed to resist spills, dirt, and everyday wear from claws and active dogs.
9. How long does installation take?
Installation is quick and simple. Most seats can be securely fitted in under a minute using adjustable straps and seatbelt attachments.
10. Do you offer fast delivery across the UK?
Yes, we provide fast UK delivery so you can receive your dog travel essentials quickly, along with easy returns and expert customer support.