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How to Choose the Right Harness Size for Your Dog — A Practical Step-by-Step Guide
A harness is one of the most popular choices among dog owners — and for good reason. Unlike collars, harnesses don't put pressure on the trachea, distribute force evenly across the chest and give better control on walks. But to do their job properly, they need to fit well. A harness that's too loose can slip off; one that's too tight will chafe and restrict movement. In this guide we show you how to measure your dog and choose the right size.
What you'll need
All you need to measure your dog is:
- a soft fabric measuring tape (not a rigid ruler),
- a piece of paper and a pen to write down the results.
Measure your dog while they're standing and relaxed — not after a run or play session when their muscles are tense.
Step 1: neck circumference
Wrap the measuring tape around your dog's neck at its widest point — usually just at the base where the neck meets the body. You should be able to slip two fingers comfortably between the tape and your dog's neck. Write down the measurement.
This measurement is especially important for harnesses that fasten at the neck — it determines whether your dog can breathe and swallow freely.
Step 2: chest circumference
This is the most important measurement for choosing a harness. Wrap the tape around the widest part of your dog's chest — just behind the shoulder blades and front legs. Again, leave a two-finger gap between the tape and your dog's body.
Note: don't measure the deepest point of the chest (from the spine to the sternum) — you want the horizontal circumference.
Step 3: back length (optional)
Some harness styles — particularly Y-shaped or Norwegian harnesses — also require a back length measurement. Measure from the base of the neck (where the body begins) to the base of the tail. This measurement helps ensure the rear strap doesn't press on the hips or restrict movement of the hind legs.
How to read a size chart
Every manufacturer uses their own size chart, so always check the measurements for the specific model — don't rely on S/M/L/XL labels, which vary between brands. Look for the chest circumference column and choose a size so that your measurements fall in the middle of the given range — not at its edge.
If your dog falls between two sizes:
- for adjustable harnesses — choose the smaller size and loosen the fastenings,
- for non-adjustable harnesses — choose the larger size,
- for puppies and growing dogs — choose the larger size with room to grow.
How to check if the harness fits correctly
Once the harness is on, do the two-finger test: slide two fingers under each strap — at the neck, behind the shoulder blades and under the belly. If your fingers slip in easily but there's not much extra room, the fit is right.
Also check that your dog can comfortably:
- lift their front legs into a normal stride,
- turn their head both ways,
- breathe without visible effort,
- sit and lie down without the harness needing to be adjusted.
The most common mistakes when choosing a harness
Measuring over the coat. For long-haired dogs, the tape should touch the skin, not rest on top of the fur — otherwise the measurement will be too large.
Guessing the size by eye. Breeds of similar weight can have very different chest builds — a Bulldog and a Border Collie may weigh the same but need completely different harnesses.
Ignoring a puppy's growth. Puppies grow fast — a harness that fits perfectly at 3 months may be too small in 6 weeks. Choose a model with a wide adjustment range or come back for a new size once your dog has finished growing.
feraw harnesses — how to order
All feraw biothane harnesses are made to order based on two key measurements: neck circumference and chest circumference. When placing your order, provide both measurements in centimetres — we'll make a harness tailored precisely to your dog, with adjustment built in for the perfect fit.
If you're not sure, get in touch — we're happy to recommend the right size based on your dog's measurements and breed.
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