Nearly every pet item that comes back is the wrong size, and nearly every wrong size comes from guessing by breed. A Labrador is not a size. Four measurements, taken once and written down, fix almost all of it.
Take these four numbers, put them in your phone, and you will never guess again: neck, chest girth, back length, and weight. Everything we sell that has a size is sized on some combination of those. Add paw width if you are buying boots.
The four measurements
| Neck | Where a collar sits, not the base of the skull |
|---|---|
| Chest girth | All the way round, right behind the front legs — the widest point |
| Back length | Along the spine, from the collar to the base of the tail |
| Weight | Hold your pet, stand on the scales, subtract yourself |
| Paw width (boots only) | Widest point, with weight on the paw |
| Between sizes | Always size up |
How to take each one
Use a soft tailor's tape. If you only have a rigid one, use a piece of string and measure the string afterwards.
Neck
Measure where a collar actually sits, which is lower than most people think — not up under the jaw and not at the base of the skull. Keep two fingers under the tape as you measure, and that spare room is already built in.
Chest girth — the one that matters most
Stand your pet up. Pass the tape around the deepest part of the chest, immediately behind the front legs, and bring it back to where you started.
This is the number that decides whether a harness, a coat or a carrier fits, and it is the one most often taken in the wrong place. Too far back and you are measuring the belly, which on most dogs is smaller — which is exactly how people end up with a harness that will not close.
Back length
From the base of the neck where a collar sits, along the spine, to the base of the tail. Not to the tip of the tail. Have your pet standing square, not sitting and not stretched out.
This is what sizes coats, jumpers and jackets. A coat sized on weight alone will be wrong for any dog that is long-backed or short-backed for its weight, which is most of them.
Weight
Stand on the scales holding your pet, then stand on them alone, and subtract. Vets' waiting rooms usually have a floor scale you are welcome to use.
Paw width, if you are buying boots
Stand your dog on paper and press the paw flat so their weight is on it — an unweighted paw is narrower and will give you boots that pinch. Mark either side of the widest point and measure between the marks.
Measure a front paw. Front paws are usually wider than back paws, so sizing to the front means all four fit.
What each product is actually sized on
| Product | Primary | Also check |
|---|---|---|
| Collar | Neck | — |
| Harness | Chest girth | Neck |
| Coat, jacket, jumper | Back length | Chest girth |
| Carrier or backpack | Weight | Back length, and height when sitting |
| Boots | Paw width | — |
| Lift sling | Weight | Waist or belly girth |
| Muzzle | Snout circumference | Snout length |
| Bed | Length nose to tail base, plus about 10 cm | How your pet sleeps |
The four mistakes behind most wrong sizes
- Guessing by breed. Two Labradors can be 25 kg and 38 kg. Breed tells you a shape, not a size.
- Measuring the belly instead of the chest. The chest is right behind the front legs, and it is bigger.
- Measuring over a thick coat, or over a flattened one. Take it on the coat your pet will be wearing, and do not pull the tape tight.
- Sizing down to get a snug fit. Between sizes, go up. A slightly large harness can be tightened; a small one cannot be made bigger.
Why the charts often run small
Most pet apparel is manufactured to Asian sizing, and a size L on those charts is commonly one to two sizes smaller than a US or European L. This is not a defect and it is not a reason to distrust the chart — it is a reason to read the numbers and ignore the letter.
Our listings give the measurements in centimeters and inches for exactly this reason. If a chart gives only letters, that is a product to be careful with.
Two fingers, and what it actually means
For anything that goes around your pet — collar, harness, muzzle — you should be able to slide two fingers flat between the strap and your pet, comfortably, with no forcing.
One finger is too tight. Three means your pet can back out of it. On a cat, that margin is the difference between a harness that holds and one that does not, because a cat's shoulder blades are not fixed to the skeleton the way a dog's are.
Growing puppies and kittens
Re-measure monthly until they are a year old. An outgrown collar is the most common cause of neck injury in young dogs, and it happens gradually enough that nobody notices.
Buy adjustable where you can, and accept that a fast-growing dog will need a second collar and harness before it is done growing. That is cheaper than the alternative.
Common questions
How do I measure my dog for a harness?
Chest girth is the number that matters — all the way around, immediately behind the front legs, which is the widest point. Check the neck measurement too, and size up if between two.
How do I measure my dog for a coat?
Back length, along the spine from the collar to the base of the tail, not to the tip. Check chest girth as well if your dog is broad.
Why do pet clothes run small?
Most are made to Asian sizing, where a size L is commonly one to two sizes smaller than a US or European L. Read the centimeter and inch measurements rather than the letter.
Should I size up or down if I am between sizes?
Always up. A slightly large harness or coat can be adjusted; a small one cannot be made bigger.
How tight should a harness or collar be?
Two fingers should slide flat underneath, comfortably. One is too tight; three means your pet can back out of it.
How do I measure a paw for boots?
Stand your dog on paper with weight on the paw, mark either side of the widest point, and measure between the marks. Use a front paw — they are usually wider than the back.
What you need, and what happens if it is wrong
The only tool on this page costs almost nothing and is not from us: a soft tailor's tape. A piece of string and a ruler works too.
| Buying | Example | Measure |
|---|---|---|
| A harness | Adjustable harness and leash set | Chest girth behind the front legs |
| A winter coat | Reflective winter coat, S–2XL | Back length along the spine |
| A collar | Adjustable nylon collar | Neck where the collar sits |
| Boots | Outdoor dog boots | Front paw width, weight on the paw |
| A carrier | Oxford carrier backpack | Weight, plus height sitting up |
| A lift sling | Rear-leg lift sling | Weight and waist girth |
If we get it wrong, or you do, it costs you nothing. Send one photo of the tape on your pet within 30 days and we send the right size — nothing to ship back, no restocking fee. We would still rather you measured first, because the right size arriving first time is a better week for your pet than two weeks of waiting.
Also worth reading: fitting a harness properly and measuring for a lift sling.
Sources
- Standard veterinary and manufacturer guidance on canine and feline measurement points for collars, harnesses and apparel
- Blue Cross and RSPCA — collar fit guidance and the two-finger rule
- Guidance on collar-related injury in growing dogs from outgrown or unchecked collars
- Comparative sizing conventions between Asian, US and European pet apparel charts
Written by Kindopet Guides. Reviewed 7 September 2026. General guidance, not veterinary advice.