Dog Harness Size Calculator
Convert chest girth and neck measurements into the right harness size, with the fitting checks that stop escapes and chafing.
The widest part of the ribcage. Measure all the way round.
Around the middle of the neck, not tight against the skull.
Harness size
M 55-70 cm
- Measured chest
- 60.0 cm
- Measured neck
- 40.0 cm
- Measure the chest at its widest point, just behind the front legs.
- Two fingers should fit under any strap. Any looser and a determined dog will back out of it.
- If chest and neck fall in different sizes, buy for the chest and adjust the neck straps.
- Y-front harnesses leave the shoulder free to move. Straps across the front of the shoulder restrict the gait.
Generic size bands
| Size | Chest girth |
|---|---|
| XS | 30–40 cm |
| S | 40–55 cm |
| M | 55–70 cm |
| L | 70–85 cm |
| XL | 85–105 cm |
| XXL | 105–130 cm |
Brands differ, sometimes a lot. Always check the manufacturer's own chart against your measurements before buying.
How this is calculated
Harness sizing is driven almost entirely by chest girth. Neck girth matters for whether the front straps can be adjusted to fit, but it does not usually determine the size you buy.
| Size | Chest girth |
|---|---|
| XS | 30–40 cm |
| S | 40–55 cm |
| M | 55–70 cm |
| L | 70–85 cm |
| XL | 85–105 cm |
| XXL | 105–130 cm |
These bands are generic. Manufacturers vary considerably, and some size by weight rather than by measurement, which is far less reliable. Always compare your measurements against the specific brand's own chart.
Fitting checks
- Two fingers flat under every strap, on a standing dog.
- The chest strap sits on the breastbone, not across the front of the shoulder joints.
- Straps behind the front legs sit a few centimeters back, not in the armpit.
- Walk the dog a few meters and check nothing rides up or twists.
Sources
- Harness sizing is the convention used across common harness ranges, which differ between makers; girth is the measurement that decides the size.
- Y-front harnesses are preferred over strap-across-the-shoulder designs on shoulder range of motion grounds. The evidence is limited, so we state it as a preference rather than a finding.
The escape test
Before the first real walk, fit the harness indoors and gently pull backwards on the lead while a second person holds the dog's attention forward. A harness a dog can reverse out of will be discovered the hard way otherwise, and it is almost always the chest strap being one notch too loose.
Coat changes the fit
A double-coated dog measured in winter will be swimming in the same harness by July. Recheck the fit after a moult or a grooming appointment, and again on any growing dog every few weeks.
Common questions
How do I measure my dog for a harness?
Chest girth is the measurement that matters: put a tape all the way around the ribcage at its widest point, just behind the front legs. Measure the neck too, lower than a collar would sit, where the neck meets the shoulders.
What if my dog is between harness sizes?
Go up, and adjust down. A harness at the top of its range has no room left, and a dog that gains a little weight or grows a winter coat then no longer fits it.
How tight should a dog harness be?
Two fingers should fit flat under any strap. Looser than that and a dog that plants its feet and backs up will escape, which typically happens beside a road at the worst possible moment.
Are harnesses better than collars for dogs that pull?
Yes. Sustained pressure on the throat from a collar is linked to tracheal damage and is a particular risk in small breeds. A harness spreads the load across the chest. It does not by itself stop pulling, which is a training matter.
What is a Y-front harness?
One where the chest strap forms a Y and sits on the breastbone, leaving the shoulder joint free. Harnesses with a horizontal strap across the front of the shoulders restrict the reach of the front legs, which matters most for dogs that run or work.
Should the lead clip on the front or the back?
Back clips suit dogs that walk politely and are more comfortable for running. Front clips turn a pulling dog back toward you, which helps during training. Many harnesses have both.