You measured your dog carefully. Their neck fits a size S, but their chest matches a size M. Which measurement should come first?
There is no answer that works for every harness. The shape of the model, its adjustment ranges and the manufacturer’s instructions should guide your choice.
First check where you measured
The neck measurement asked for a harness is not necessarily the one for a collar. Likewise, the point where you measure the chest must match the diagram for the chosen model.
Measure again with your dog standing. Write the figures down in centimetres and check that you have not added a margin the manufacturer has already allowed for.
If two measurements give very different results, start again before choosing a size.
Look for a size that fits every required measurement
Look at the full adjustment ranges, not just the letters S, M or L.
For example, if a size fits the chest but its smallest neck opening is still too wide, it is not automatically suitable. Conversely, choosing the smaller size solves nothing if it cannot properly fit the rib cage.
Weight and breed can give context, but they do not replace measurements.
Should you always go up a size?
No. Even with a single manufacturer, the advice can vary by model: Ruffwear says to choose the larger size for its Front Range and the smaller size for some configurations of its Web Master. So you need to check the page for the exact harness.
Source: Front Range guide
Source: Web Master guide
For a puppy, buying much too big “to grow into” does not guarantee a good fit today.
What should you send the seller if you are unsure?
Send the measurements, the name of the model you are considering and, if it helps, a photo of your dog standing side-on. Say whether they are still growing and which measurement is causing the problem.
If no size properly covers the dimensions needed, another cut or a model with more adjustment will sometimes be better.
Before personalising a patch, also check the size exchange conditions: it is better to settle any doubt before you order.
Read also
- How to measure your dog for a harness without a tape measure: to take the measurements again step by step.
- How to put a harness on your dog: step-by-step method: to check the fit once the size is chosen.
- Puppy harness: from what age and how to get them used to it?: if your dog is a puppy who is still growing.