How to Measure Your Dog for a Harness
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Chest girth is the measurement that decides most harness sizes, and it takes about five minutes with a soft tape and a few treats. Breed labels and "small, medium, large" are much less reliable, because sizes vary between brands and between dogs of the same breed. Do the measuring first, then compare the numbers against the maker's own size chart.
You will need a soft tape measure (a piece of string and a ruler works too), a few treats, and a second person if your dog fidgets.
Steps
- Get the dog standing square. Stand the dog on all four feet, on a flat floor, with its head up and relaxed. A dog sitting or slumping will give you a smaller reading than it should. Treats help here.
- Measure the chest girth. Wrap the tape around the deepest part of the ribcage, just behind the front legs. It should go round the whole chest, over the shoulder blades on top and across the breastbone underneath. Keep the tape level, not twisted. It should be snug but not tight, with room to breathe.
- Measure the neck. Some designs, including many Y-shaped ones, also refer to neck size. Measure where a collar would normally sit, at the base of the neck, and allow the same snug-but-not-tight fit.
- Note the weight. Many size charts also list a weight range. Weigh your dog at a vet's surgery or on home scales if you can, but treat weight as a cross-check rather than the main figure.
- Compare with the maker's chart. Look at the chart for the exact model you are buying, not a different range from the same brand. If you land between two sizes, read the maker's advice, and check the adjustment range of each.
- Fit-check once it arrives. Put the harness on and adjust every strap, then follow the two-finger rule below.
The two-finger fit check
Once the harness is on and adjusted, you should be able to slide two fingers flat between the strap and your dog's body at the chest and around the girth. If you can fit a whole hand, it is probably too loose and could twist or let the dog back out. If you struggle to get one finger in, it is too tight. Check around the neck, behind the front legs and along the belly strap.
Then walk the dog around the house, on the lead, for a few minutes. Watch for the harness riding up, shifting to one side, or restricting how the front legs move. Most dogs need a few days to get used to wearing one, so give your dog time to settle. Our guide to introducing a dog to a harness covers this.
What the three listings give you
The listings for three popular harnesses show how different the sizing information can be.
- The JULIUS-K9 IDC Powerharness listing is the most specific. For the medium it gives a chest circumference of 58-76 cm and a dog weight of 14-25 kg.
- The Ruffwear Hi & Light listing we looked at is for the XXXS and mentions 23-33 cm alongside it, with four points of adjustment. The listing does not say exactly what that figure refers to, so use Ruffwear's size chart.
- The PetSafe Easy Walk listing says only "large", though it also lists four adjustment points. You will need the maker's chart to work out whether your dog fits. The listing also says international products may differ in fit, so check who is selling it.
When things go wrong
- Between sizes. Many dogs fall in the gap. A harness with more adjustment points gives more room to fine-tune, but one that is adjusted to its extremes can still fit badly.
- Thick coats. A fluffy coat can hide the true chest measurement. Press the tape gently so you are measuring the dog, not just the fur, then judge how much padding the coat adds.
- Growing dogs. Puppies can outgrow a harness within weeks. Re-measure every few weeks during fast growth, and again if your dog gains or loses weight.
- Mixing up brands. A medium from one maker is not a medium from another. Use the chart each time.
- Not re-checking. Straps loosen with use. Run through the two-finger check every so often.
When to stop and ask for help
If you see rubbing, sore patches, hair loss under the straps, or your dog freezes, flinches or tries to back out of the harness, take it off. Ask a vet if the skin looks irritated, and a trainer or the retailer's customer service if it is a fit issue. For help choosing a style after you have your numbers, our guide to the best dog harnesses in the UK is a place to start.
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