A harness only works if it fits. Getting the size right takes about two minutes and a soft tape measure. If you do not have one, use a piece of string and hold it against a ruler afterwards.
What to measure
Measure while your dog is standing on all four legs.
- Chest girth. Wrap the tape around the widest part of the ribcage, just behind the front legs. This is the number that matters most for a harness.
- Neck girth. Measure around the base of the neck, where a collar sits. Some harnesses list this as well.
- Weight. Step on a scale holding your dog, then subtract your own weight. Weight ranges are a guide. Go by the chest and neck measurements when they disagree.
Keep the tape snug, not tight. You should be able to slide two fingers under it.
Reading the size table
Sizes are not standard between brands, so a medium in one harness can be a large in another. Always use the table for the harness you are buying. Size ranges often overlap. If your dog falls between two sizes, choose the larger one and take in the straps.
Trailhead No-Pull Harness
| Size | Chest girth |
|---|---|
| S | 15.7 to 23.6 in (40 to 60 cm) |
| M | 21.7 to 27.6 in (55 to 70 cm) |
| L | 26 to 35.4 in (66 to 90 cm) |
| XL | 30.7 to 41.3 in (78 to 105 cm) |
See the Trailhead No-Pull Harness.
Basecamp Tactical Harness
| Size | Neck girth | Chest girth | Dog weight |
|---|---|---|---|
| L | 18 to 29 in (46 to 74 cm) | 24 to 37 in (61 to 94 cm) | 50 to 80 lb (23 to 36 kg) |
See the Basecamp Tactical Harness.
Checking the fit when it arrives
- Two fingers. You should be able to slide two fingers under every strap. Fewer and it is too tight. A whole hand and it is too loose.
- Behind the front legs. The chest strap should sit a little behind the legs, not in the armpit, where it can rub.
- No backing out. With the harness on, hold the leash and step behind your dog. If the harness slides forward over the shoulders, tighten it or go down a size.
- Check again after a few walks. Straps can loosen with use.
Try it on indoors first. Our returns cover unused gear in its original packaging for 30 days, so do the fit check before the first muddy walk.
Puppies and growing dogs
Measure again every few weeks. A harness that fit last month may not fit now. If your puppy is at the top of a size range, the next size up will last longer.
Still between sizes?
The full size guide has measurements for everything we sell. Or send us a message with your dog's breed, weight and chest measurement, and we will help you pick.