Most returns in this category are size returns, and almost all of them come from measuring the wrong thing. Two numbers — neck and girth — decide every collar and harness you will ever buy. Here is how to take them properly, and what to do when your dog lands between sizes.
You need three measurements, and only two of them are hard
Write these down once and keep them in your phone. They change slowly in an adult dog, and having them saved turns every future purchase into a thirty-second decision.
| Measurement | Where | Used for |
|---|---|---|
| Neck | Base of the neck, where a collar naturally settles — lower than the throat, just above the shoulders | Collars |
| Girth | Around the deepest part of the chest, immediately behind the front legs | Harnesses |
| Length | Nose to the base of the tail, dog lying stretched out on their side | Beds, carriers, crates |
No soft tape measure?
Use string. Wrap it, mark where it overlaps, then lay it flat against a ruler. It is exactly as accurate as a tailor’s tape, and most households have string.
Collars: neck plus two fingers
Run the tape around the base of the neck and pull it snug, not tight. Then add the width of two fingers. That is your collar size.
The two-finger rule is not folklore — it is the amount of slack that lets a collar sit comfortably without being loose enough to pull over the ears. Test it after fitting: you should be able to slide two flat fingers between the collar and the neck, and not a third.
If your measurement falls between two sizes, take the larger one. Collars adjust down far more comfortably than they adjust up. Our Harbor Reflective Collar runs Small 10–14 in, Medium 14–19 in and Large 18–25 in, with deliberate overlap between sizes for exactly this reason.
Puppies are a special case
A puppy will outgrow their first collar, and possibly their second. Buy at the smaller end of the adjustment range and check the fit weekly — a collar that was correct a fortnight ago can become genuinely tight on a fast-growing large breed. Do not buy oversized “to grow into”; a loose collar comes off at the worst moment.
Harnesses: girth decides everything
This is where most people go wrong, because harness charts often list weights and breeds and people use those instead of measuring.
Weight tells you almost nothing about chest circumference. A 40 lb whippet and a 40 lb French bulldog need different harness sizes, and neither matches a 40 lb beagle. Breed is barely better — two Labradors from different lines can be two sizes apart.
Measure the girth. Stand your dog square, find the deepest part of the ribcage just behind the front legs, and take the circumference there. That number, and only that number, picks the size.
Between sizes? Size up.
A good harness has independent adjustment at the neck and girth on both sides, which means the larger size can be taken in. The smaller size cannot be let out beyond its maximum. The Harbor No-Pull Harness has four adjustment points and roughly four inches of travel within each size band, so sizing up is almost always the safer error.
The two-finger check, again
Once the harness is on, you should be able to slide two flat fingers under the girth strap and no more. This is the single most important fitting check, and the one people skip.
- Too loose and a determined dog will back out of it — reversing while lowering the head is a manoeuvre most dogs work out within a month of wearing a loose harness.
- Too tight and it rubs behind the elbows, which is where you will see the hair thin first.
A quick sanity check before you order
| You measured the throat, not the base of the neck | Re-measure lower. The throat is narrower and gives you a collar that slips over the ears. |
|---|---|
| Your dog held their breath or sucked in | Measure twice, a minute apart, and take the larger reading. |
| You measured a wriggling puppy | Have a second person hold and reward. A tense dog stands differently. |
| You measured over a thin summer coat | Add up to an inch of girth for a double coat in winter, or pick the size with more adjustment left. |
If it still comes out wrong
Sizing from a measurement is not perfect and no honest shop pretends otherwise. Our size exchanges are free in both directions within 30 days — we send a prepaid label and ship the correct size as soon as the first is on its way back. Full detail is in our returns policy, and every size band we stock is laid out on the size guide.
If you would rather not guess at all, email the measurement, breed and weight to support@accesspet.store and we will tell you which size to order.