How to Measure Your Dog for a Collar or Harness

Finding the right size collar or harness is important for your dog’s comfort and safety. A product that is too tight may cause rubbing or restrict movement, while one that is too loose may slip off during a walk.

The good news is that measuring your dog only takes a few minutes.

What You’ll Need

Prepare:

A soft measuring tape
Your dog
A few treats to help them stay still

If you do not have a measuring tape, use a piece of string and measure it against a ruler afterward.

How to Measure Your Dog for a Collar

Wrap the measuring tape around the part of your dog’s neck where the collar normally sits.

The tape should feel snug, but it should not press tightly into the fur or skin.

Use the two-finger rule: you should be able to slide two fingers comfortably between the measuring tape and your dog’s neck.

Record the measurement in centimetres or inches, then compare it with the product’s size chart.

Measuring tips

Measure your dog while they are standing.
Do not measure an old collar, as different products may fit differently.
For dogs with thick or fluffy fur, gently press the tape through the coat without pulling it too tightly.
If your dog is between two sizes, choosing the larger adjustable size is usually safer.

How to Measure Your Dog for a Harness

Harness sizing may require two or three measurements, depending on the design.

1. Measure the chest girth

The chest girth is usually the most important measurement.

Wrap the measuring tape around the widest part of your dog’s rib cage, just behind the front legs.

Keep the tape level and make sure it is snug without being tight.

2. Measure the neck

Measure around the lower part of the neck, near where the neck meets the shoulders.

This position may be lower than where a regular collar sits, especially for step-in or vest-style harnesses.

3. Measure the back length if required

Some harnesses, jackets and clothing also require a back-length measurement.

Measure from the base of the neck to the base of the tail while your dog is standing naturally.

Always check the individual product size guide, as not every harness uses the same measurements.

How Should a Harness Fit?

A properly fitted harness should:

Sit securely without twisting
Allow your dog to walk and run naturally
Leave enough space for two fingers under the straps
Stay clear of the throat
Avoid rubbing behind the front legs
Remain secure when your dog moves backwards

After fitting the harness, gently pull it in different directions. It should stay in place without slipping over your dog’s head or shoulders.

Signs the Collar or Harness Is Too Tight

The product may be too tight if:

It leaves red marks or indentations
Your dog scratches or bites at it
Your dog appears uncomfortable
The straps rub behind the legs
You cannot fit two fingers underneath
Your dog’s movement seems restricted

Signs It Is Too Loose

The product may be too loose if:

It rotates excessively
Your dog can pull their head out
The harness shifts sideways
The straps hang away from the body
Your dog can back out of it
The collar can slide over the ears

A loose collar or harness may look comfortable, but it can become a serious safety risk outdoors.

Puppies and Growing Dogs

Puppies grow quickly, so check the fit regularly.

Depending on your puppy’s age and breed, you may need to remeasure them every few weeks. Adjustable collars and harnesses can provide extra growing room, but they should still be checked before every walk.

Do not assume the product still fits just because your puppy can still wear it.

Check the Size Chart Before Ordering

Pet product sizing is not always consistent between brands. A medium size from one company may be different from a medium size from another.

Always use your dog’s actual measurements and compare them with the specific product size chart.

Breed and weight can be useful references, but they should not replace proper measurements. Dogs of the same breed may have very different body shapes.