How to Measure Your Dog for a Harness (and Why It Matters)

Measuring for the Perfect Fit! Ensuring your golden retriever is comfortable and secure in their harness starts with the right measurements.

Getting the right harness size is the difference between a product that works and one that causes rubbing, slipping, or discomfort. A harness that fits well should be secure without being tight, sit flat against the chest, and allow full natural movement. One that doesn’t fit will chafe, rotate under the dog’s belly, or slip over the head - none of which is ideal on a busy pavement.

What You Need

A soft measuring tape (the kind used for sewing) or a length of string and a ruler. That is it. Do not use a metal tape measure - the rigid edge is uncomfortable against a dog who has decided they would rather be somewhere else.

How to Measure: Chest Girth

This is the primary measurement for harness sizing. Wrap your tape around the widest part of your dog’s chest - directly behind the front legs, where the harness chest plate sits. Pull it snug but not tight, and note the measurement in centimetres. Add 2-3cm to this number to give the harness room to sit comfortably without pressure.

How to Measure: Neck

Some harnesses also require a neck measurement for the top strap. Measure the circumference of your dog’s neck at its widest point, again adding 2cm for comfort. This is less critical than chest girth for most harness styles, but matters for step-in harnesses and some active harness designs.

Reading Our Size Chart

Our size chart gives a chest girth range for each size, alongside typical breeds and approximate weight. The breed column is a guide, not a rule - individual dogs within the same breed can vary considerably. Always use the tape measure. A French Bulldog’s proportionally broad chest often sizes them up relative to their weight, while a Whippet’s narrow, deep chest can run small.

If Your Dog Is Between Sizes

Choose the larger size. A harness that is slightly large can be adjusted to fit properly. A harness that is too small cannot be made larger, will dig in, and will cause exactly the kind of rubbing that makes a dog resist wearing it.

Signs the Harness Doesn’t Fit

Too tight: you cannot slide two fingers flat between the harness and the dog’s body. Too loose: the

harness rotates under the belly, the back ring slides to one side, or the front clip hangs below the sternum. Chafing: hair loss, redness, or skin irritation in the armpit area or behind the front legs. In any of these cases, try the next size or email us at hello@thepetassembly.co.uk - we will advise.

If you are still unsure which size to order, email us at hello@thepetassembly.co.uk with your dog’s chest measurement and the harness you are considering. We will tell you exactly which size based on our experience with that specific product. We would rather answer one email than process one return.