You want your dog to be comfortable and safe on walks, and a well-fitted harness is the best way to do that. But if the harness is too loose, your dog can slip out. Too tight, and it can rub or restrict movement. The good news is that measuring your dog at home is simple and takes just a few minutes. All you need is a soft measuring tape (the kind used for sewing) and a treat to keep your pup still. Here is exactly how to measure a dog for a harness, step by step.

What You Will Need

Before you start, gather these items: a flexible cloth or plastic measuring tape, a piece of string if you do not have a tape (you can measure the string against a ruler later), and a notepad to write down the numbers. It is also helpful to have your dog standing on a flat, non-slip surface. If your dog is wiggly, have a second person help hold them still or offer a few kibble rewards. Avoid using a metal tape measure, as it is hard to bend around a dog’s body and can be uncomfortable.

Step 1: Measure the Neck Girth

The neck girth is the circumference of your dog’s neck where a collar would normally sit. To get this measurement, place the tape measure around the base of the neck, just above the shoulders. It should be snug but not tight, you should be able to slide two fingers comfortably between the tape and your dog’s fur. Write down this number. This measurement is critical because a harness that is too loose on the neck can allow your dog to back out of it. For large breeds like the Cane Corso, a well-fitted harness is especially important to prevent escape, and you can also explore Are Cane Corsos Good Family Dogs for more on their temperament and handling needs.

Step 2: Measure the Chest Girth (The Most Important One)

The chest girth is the widest part of your dog’s ribcage, just behind the front legs. This measurement determines how the harness will fit around the body. To measure, wrap the tape around the deepest part of the chest, right behind the elbows. Make sure the tape is level all the way around and not twisted. It should feel snug but not constricting. Again, the two-finger rule applies. This number is often the deciding factor between harness sizes, especially for deep-chested breeds like the Cane Corso. If your dog has a large chest, you might also be interested in Reduce Neck Strain: Best Dog Bowls for Cane Corsos to support their posture during meals.

Step 3: Measure the Length (Optional but Helpful)

Some harness styles, particularly step-in or vest types, also require a back length measurement. This is the distance from the base of the neck (between the shoulder blades) to the base of the tail. Have your dog stand straight, and measure along the spine. This helps you avoid a harness that is too long and rubs the belly or too short and pulls on the shoulders. For active, intelligent breeds like the Australian Shepherd, a harness that allows full range of motion is key. You can read more about their exercise needs in Are Australian Shepherds Good Family Dogs.

Pro Tip

If your dog is between sizes, always choose the larger size. You can tighten most harnesses with adjustable straps, but you cannot make a too-small harness bigger. Also, measure your dog every few months if they are still growing or if their weight changes.

How to Use Your Measurements to Choose the Right Harness Size

Once you have the neck girth and chest girth numbers, compare them to the manufacturer’s size chart. Every brand is different, so do not assume your dog’s weight alone is enough. A 50-pound dog with a deep chest might need a large in one brand and a medium in another. Look for a harness that has at least two points of adjustment (neck and chest) for the best custom fit. When you first put the harness on, check that it does not shift side to side and that the D-ring on the back sits centered between the shoulder blades. If the harness rubs under the armpits, it is likely too small or the straps are not adjusted correctly.

Common Measuring Mistakes to Avoid

  • Measuring while your dog is sitting or lying down. Always measure with your dog standing on all four paws for the most accurate numbers.
  • Using a rigid ruler or tape. This cannot conform to the curves of your dog’s body and will give you a wrong measurement.
  • Pulling the tape too tight. The tape should sit against the fur without digging in. If you see the skin indenting, loosen it.
  • Forgetting to check the fit after a few walks. Some harnesses stretch or settle over time. Recheck the fit after the first week.

A well-fitted harness should let your dog move freely without restriction, and you should be able to fit two fingers under any strap.

Special Considerations for Different Dog Breeds

Breed conformation matters. For example, Cane Corsos have broad chests and thick necks, so look for a harness with a wide front strap and plenty of adjustment room. The same goes for their feeding setup, you can find Recommended Dog Food for Cane Corso Puppies to support their growth. Australian Shepherds, with their deep chests and active nature, benefit from a harness that does not restrict shoulder movement. For mental stimulation during downtime, consider Puzzle Toys for Australian Shepherds: Top Picks for Smart Dogs. If your dog is a heavy puller, choose a front-clip harness to discourage pulling without choking. And if your dog has a sensitive neck or trachea, a harness is always better than a collar.

How to Test the Fit Before You Buy

If you are shopping online and are unsure about the size, look for retailers with a good return policy. Some brands offer a fit guarantee. When the harness arrives, try it on your dog indoors for a few minutes. Watch for signs of discomfort like scratching, biting at the harness, or trying to roll on the ground. Take your dog for a short walk and see if the harness stays in place. If it slides to one side or rides up into the neck, it is not the right size or style. A properly fitted harness should stay put and allow your dog to trot, sit, and lie down without resistance.