Finding your dog between two harness sizes can be frustrating. The smaller size may technically fit at the top of its range, while the larger size begins only a little above that measurement.
The answer is not automatically to choose smaller or larger. Look at the complete adjustment range, your dog’s body shape and how much room you need for future changes.
Measure again before deciding
When you are close to a size boundary, a small measuring error matters more. Measure the widest part of the chest again with the tape level around the body.
If possible, take the measurement twice while your dog is standing naturally.
Check where the measurement sits in the smaller range
If your dog is already at the absolute maximum of the smaller size, there may be very little room left to adjust.
That can become relevant for coat changes, normal body changes or simple fine tuning.
Check whether the larger size tightens enough
A larger size is only useful if it can still be adjusted securely around your dog.
If the harness creates large gaps even at the smallest setting, larger is not the better choice simply because it gives more room.
Body shape can break the tie
A dog with a broad chest and narrow neck may need different adjustment room from a dog with more even proportions.
Look at how much adjustment each size offers around the neck and chest, not only the main chest number.
Think about puppies and growing dogs
If your puppy is still growing, extra adjustment room can be useful. That does not mean buying a harness that is currently too large.
The harness still needs to fit securely today.
Seasonal coat changes
Long haired dogs can measure slightly differently through the year. If your dog develops a thick winter coat, leave enough adjustment room to fine tune the fit.
Do not choose smaller just to stop movement
A harness that is too small can sit too close to the front legs, press on the chest or limit shoulder movement.
Secure does not mean restrictive.
Do not choose larger only for comfort
A harness that is too large can rotate, ride up or leave large gaps.
Comfort comes from the correct size and adjustment, not from extra loose space.
Use movement as the final test
Once the harness is adjusted, let your dog walk, turn and sniff. Watch whether it stays centred and clear of the throat.
The shoulders should move naturally and the rear strap should stay clear of the front legs.
What if both sizes seem possible
Compare how close each option sits to the ends of its adjustment range. The size that leaves useful room for fine tuning while still fitting securely is usually the more practical choice.
UNBORINGBYPIP sizing approach
Our general guidance is to choose the larger size when your dog is genuinely between two sizes, provided that the larger size can still be adjusted securely around your dog.
Use our dog harness measuring guide and the product size chart before deciding.
Size charts are the start, not the finish
The measurement gets you into the right range. The actual fit comes from adjusting the harness to your dog and checking it during movement.