A harness that is too loose will slip off, a harness that is too tight will pinch. Determining the correct size for a puppy that is still growing is slightly more difficult than for an adult dog. With this guide you can measure the right size in a few minutes, and you'll know exactly when to scale up.
What do you need?
A flexible measuring tape (or a piece of string and a ruler) and a few minutes of patience from your puppy, a handful of snacks helps.
Measure the right size in 3 steps
- Chest circumference. Measure around the widest point of the chest, just behind the front legs.
- Neck circumference. Measure loosely around the base of the neck, where a collar would normally sit.
- Compare with the size chart. View our size guide for the exact measurements per harness.
Take growth into account
A puppy can grow a lot in just a few weeks. Therefore, choose an adjustable harness with space in multiple directions, and check the fit every 2 to 3 weeks. A good rule of thumb. you should be able to slide two fingers flat between the harness and the skin, no more, no less.
This way you measure accurately (and avoid the wrong size)
- Measure at a time when your puppy is standing quietly, not just after running or playing, as the chest will expand differently.
- Do not pull the measuring tape tightly. Loose, but not loose enough to shift.
- Measure twice and take the average if the results differ slightly.
- Does your puppy have a thick coat? Then measure across the coat, as the harness will also fit over the coat.
What you should not do
- Don't just buy a size bigger to grow into. A harness that is already too loose can shift or even slip off while walking.
- Don't rely on the size of a collar. Neck size and chest size are not in a fixed relationship, especially in puppies that are still growing.
- Don't skip rechecking because the harness still fits. Puppies grow in spurts, not evenly.
- Don't ignore red spots or chafing, even if they seem small. That is a signal to immediately scale up a size.
Frequently asked questions
What if my puppy falls between sizes?
Then choose the smaller of the two sizes, provided your harness has enough adjustment space to grow with you.
How often should I recheck the size?
Up to about 8 months we recommend checking the fit every 2 to 3 weeks. Larger breeds often grow faster and deserve a check a little more often.
What are the signs that the harness is too small?
Red spots, chafing, or a harness that is visibly tight around the body without room for two fingers.
And signs that it is too big?
The harness rotates around the body when walking, or your puppy can slip through it with a paw. Then it's time to size down or make additional adjustments.
Do I have to measure again if I change brands?
Yes. Size charts differ per brand and model, so a size M for one harness is not automatically the same for another.
Still in doubt? View our full size guide or choose from our adjustable puppy harnesses.
Continue with our puppy dog harnesses.
