Roughly one in five pet accessories bought online is sent back, and the single biggest reason is sizing. Not quality. Not delivery. Sizing.
The reason is simple: a "Medium" from one brand is a "Large" from another, because there is no shared standard. Manufacturers set their own size charts, and a chart built around a Beagle will not fit a Dachshund with the same chest measurement. If you buy by the letter on the label, you are guessing.
Two minutes with a soft tape measure removes the guesswork entirely.
What you need
A soft tailor's tape, the kind used for sewing. If you do not have one, use a piece of string and then lay it flat against a ruler. A rigid metal builder's tape will not follow the curve of a dog's chest and will give you a reading that is too small.
Measuring for a collar: the neck
- Have your dog standing, not sitting. Sitting changes the shape of the neck and adds slack.
- Run the tape around the base of the neck, where a collar would naturally sit — lower than the jaw, just above the shoulders.
- Keep the tape snug against the coat, not compressing it.
- Read the number, then add 2 to 3 cm for a small dog, or 3 to 5 cm for a large one.
That final number is your collar size. Buy the size range that contains it, and if you fall between two ranges, size up — a collar that is slightly loose can be tightened, one that is too small is useless.
The two-finger rule
Once it is on, you should be able to slide two fingers flat between the collar and your dog's neck. One finger means it is too tight. Four means your dog can back out of it, which is how dogs get lost.
For puppies, check this every two weeks. They outgrow collars faster than most owners expect, and an outgrown collar is a genuine safety problem rather than an inconvenience.
Measuring for a harness: the chest
Harnesses are sized on girth, which is the measurement around the widest part of the ribcage — right behind the front legs. This is the number that matters, and it is the one most people skip.
- Stand your dog square, weight on all four legs.
- Bring the tape around the body just behind the armpits, at the deepest point of the chest.
- Keep it level — a tape that slopes will read short.
- Take the neck measurement too, since most harnesses adjust at both points.
If your dog is between sizes on girth, size up. Harness straps almost always adjust downward further than they adjust up.
Why weight-based sizing is unreliable
Many charts list a weight range instead of measurements, and weight is the weakest possible proxy for shape. A 12 kg Beagle is barrel-chested. A 12 kg Whippet is not. Same weight, completely different girth. If a chart offers you only a weight range, treat it as a rough starting point and look for the measurement in centimetres before you buy.
Deep-chested breeds — Greyhounds, Whippets, Dobermans, Boxers, Setters — are where weight-based sizing goes most wrong. So are breeds with a lot of coat, where the tape reads the fur rather than the dog.
Measuring a long-coated dog
With a Husky, Chow, Samoyed or Collie, press the tape gently through the coat until you feel the ribcage. Measure the dog, not the fluff. Coat compresses under a harness anyway, so a measurement taken over the top of it will leave you with something that slides around.
Write it down
Keep the neck and girth measurements in a note on your phone. You will use them every time you buy anything that fastens — collar, harness, coat, life jacket — and having them saved is the difference between ordering confidently and ordering twice.
A note on cat collars
The measuring method is the same, but the hardware is not negotiable: a cat collar must have a breakaway clasp that opens under pressure. Cats climb, and a collar that does not release is a strangulation risk. If a cat collar does not clearly state that it is breakaway or quick-release, do not buy it, regardless of how well it fits.
Our own sizing
Every sized product we sell lists its measurements in centimetres, not just a letter. Where we only stock one size, we say so plainly rather than showing you options that do not exist. If a measurement is missing from a product page, email info@foldiva.com and we will measure the item and add it.
And if something arrives and the fit is wrong, you have 14 days to withdraw from the purchase without giving a reason, under EU Consumer Rights Directive 2011/83/EU. The details are in our Refund Policy.