A harness only does its job — spreading lead pressure off the throat and stopping your dog slipping free — if it actually fits. Yet sizing is where most online harness purchases go wrong: too loose and your dog wriggles out mid-walk, too tight and it chafes or restricts movement. The good news is that measuring your dog properly takes five minutes and a soft tape, and it makes buying online far less of a gamble. Here's how to get it right.
What You'll Need
Grab a soft fabric measuring tape — the kind used for sewing. If you only have a rigid builder's tape, use a piece of string instead, then lay it flat against a ruler afterwards. It helps to have a second person to keep your dog standing still, and a few treats never hurt. Measure your dog standing squarely on all four legs, not sitting or lying down, so the numbers reflect a natural walking posture.
The Two Measurements That Matter
Almost every harness is sized on one key measurement, with a second as a useful cross-check:
- Chest (girth): the most important one. Measure right around the widest part of the ribcage, just behind the front legs. Keep the tape snug but not tight.
- Neck (base): measure around the base of the neck where a collar would sit, at the point where the neck meets the shoulders — not up near the ears.
Note both numbers in centimetres. Chest girth is what most size charts key off, so it's the figure to trust when a dog falls between sizes.
How to Use a Size Chart
Every brand's sizing is a little different, so always check the specific product's chart rather than assuming your dog is a "medium" everywhere. Match your chest measurement to the range listed, and follow two rules:
- If your dog is between two sizes, size up. A slightly larger harness with the straps taken in fits better than a smaller one stretched to its limit.
- Check the range, not just a label. A 45 cm chest might be the top of a size Medium on one harness and the bottom of a Large on another.
Look for an adjustable harness with multiple strap points — it gives you room to fine-tune the fit and to allow for a growing pup or a seasonal change of coat.
The Two-Finger Fit Test
Once the harness is on, you should be able to slide two fingers flat under any strap — snug enough that it won't shift or twist, loose enough that it doesn't dig in. Walk your dog around the house and watch for chafing behind the legs, straps riding up into the armpit, or any sign your dog can back out of it. Re-check the fit after the first few wears, as straps can settle and stretch slightly with use.
Puppies and Growing Dogs
If you're buying for a puppy, expect to size up more than once as they grow. Rather than buying an expensive harness they'll outgrow in months, choose an affordable, highly adjustable style now and re-measure every few weeks. A harness that's too big "for them to grow into" is a slipping hazard today, so fit to the dog you have, not the one they'll become.
A Well-Sized Pick to Start With
Reflective No-Pull Dog Harness (Adjustable, All Sizes) — from $33.99
Best for: everyday walks across small to large dogs. An adjustable chest strap makes dialling in the fit easy, the reflective stitching adds visibility on early-morning and after-dark walks, and the chest-clip design helps discourage pulling by turning your dog gently back towards you rather than choking the throat.
Harness Sizing FAQs
Should I measure over my dog's coat?
Measure against the body for an accurate girth, but if your dog has a thick double coat, allow a little extra room so the harness isn't compressed against the fur. Re-check the fit after grooming or a seasonal moult.
My dog is between two sizes — which do I pick?
Size up, then tighten the adjustable straps. A harness at the bottom of its size range with room to loosen beats one stretched to its maximum.
How do I know the harness is too tight?
If you can't fit two fingers under the straps, it's rubbing the skin, or it's leaving a mark in the coat, it's too tight. A correctly fitted harness leaves no red marks and doesn't restrict the shoulders.
Collar or harness for a puller?
A well-fitted harness is kinder for dogs that pull, as it keeps pressure off the neck. For more on that, our guide comparing a dog harness vs collar goes into detail.
Shop Dog Harnesses at OzPetCo
Once you've measured up, browse our dog harness range — adjustable, no-pull and everyday styles for every size, with fast Australian delivery and free shipping over $99. Measure first, size up if in doubt, and that two-finger test will see you right.
