How to Measure Your Dog Correctly for a Harness (No Guessing Required)

“I’ll just buy a medium, he looks like a medium.”

Famous last words before your dog either performs a miraculous reverse Houdini escape in the middle of a busy street, or refuses to walk because their armpits are completely chafed.

When it comes to buying a harness for a dog that pulls, the model is important, but the fit is absolutely critical. An ill-fitting harness is useless at best, and dangerous at worst.

The Tools You Need

• A soft measuring tape (like the ones used in sewing).
• If you don’t have one: Use a piece of string, wrap it around your dog, mark the spot, and then measure the string flat with a ruler or stiff measuring tape.
• Treats: Because making your dog stand still while you wrap things around them is much easier if they are getting paid for their time.

Step 1: Measuring the Deep Chest (Girth)

This is the single most important measurement for 99% of harnesses on the market. If you get this wrong, the harness won’t fit.

1. Get your dog to stand up (not sit, not lay down).
2. Find the widest, deepest part of their rib cage. This is usually just a couple of inches behind their front legs.
3. Wrap the tape measure completely around this part of the chest. It should be snug, but not tight enough to indent the fur or skin.
4. Record the number in both inches and centimeters, as brands vary on their sizing charts.

💡 Sizing Tip: If your dog’s chest girth is exactly on the border between two sizes (e.g., they measure exactly 28 inches, and Medium is 22-28”, while Large is 28-34”), always size up. A larger size adjusted inwards will fit much better and prevent armpit chafing compared to a smaller size stretched to its absolute maximum limit.

Step 2: Measuring the Neck

Not all harnesses require a neck measurement (many step-in or standard Y-harnesses are highly adjustable at the front), but premium options like the Ruffwear Front Range often do.

1. Do not measure where a standard collar sits right at the top of the neck.
2. Instead, measure the lower neck, where the neck slopes down and meets the shoulders.
3. Again, the tape should be snug but not tight.

Step 3: Checking the Fit (The “Two-Finger Rule”)

Once your new harness arrives, putting it on is only half the battle. You must adjust the straps properly.

1. Symmetry is key: Adjust the left and right straps equally. If one is tighter than the other, the harness will slide to the side, shifting the front clip off the sternum and into the armpit, completely breaking the anti-pull mechanics and causing your dog to walk lopsided.
2. The Two-Finger Rule: You should be able to slide exactly two fingers flat between the harness strap and your dog’s body at any point. If you can only fit one tightly, it’s too snug. If you can fit your whole hand, it’s too loose.
3. The Armpit Check: Ensure the straps behind the front legs have at least 1 to 2 inches of clearance from the actual armpit. If it rubs right against the armpit, you risk severe friction burns during a walk.

What if it Still Doesn’t Fit?

If you measure perfectly and it simply looks “wrong” on your dog, don’t force it. Deep-chested breeds like Greyhounds, Dobermans, or Pointers sometimes struggle with standard sizing, while stocky barrel-chested breeds like Bulldogs have the opposite problem.

If this happens, return it and look for highly adjustable models, or specifically seek out an escape-proof harness for fearful dogs padding which often features a third belly strap that tackles weird shapes brilliantly.