What Harness Size Should I Choose for My Dog?

This is, by far, the most common question we get. The answer fits in one sentence: you don't choose a harness size from your dog's breed or weight — you choose it from their chest girth. Here's why, and how to do it.

Why weight and breed aren't enough

Two 26 lb dogs can differ by 3 inches in chest girth. A 26 lb French Bulldog is massive and compact; a Whippet of the same weight is lean and deep-chested. The same "size M" harness will fit one perfectly and be unusable on the other.

The "by breed" charts you find everywhere are statistical averages. They're useful for a rough first idea, never for placing an order.

The two measurements to take

Grab a flexible tape measure. Don't have one? A piece of string and a ruler will do just fine. Measure your dog standing and relaxed, on all four legs.

1. Chest girth — the decisive measurement

Wrap around the chest at its widest point, just behind the front legs. This measurement determines the harness size. If your two measurements fall into different sizes, the chest always wins.

2. Neck — for the fit

Wrap the tape around the base of the neck, where a collar naturally sits: above the shoulders, not under the jaw.

The size chart

Size	Chest girth	Neck
XS	13 – 16"	8 – 11"
S	16 – 20"	11 – 14"
M	20 – 25"	14 – 18"
L	25 – 31"	18 – 22"
XL	31 – 37"	22 – 26"

Find all the detailed charts, including for collars and coats, in our complete size guide.

The two-finger rule

Once the harness is on, you should be able to slide two flat fingers between the strap and your dog's body. Not more, not less.

• Too tight: restricts breathing and causes chafing under the front legs.
• Too loose: your dog can back out of it — the #1 cause of dogs slipping loose on walks.

The 4 most common mistakes

1. Measuring over a thick coat. On a Husky or Collie, lightly compress the coat to find the actual body.
2. Measuring a sitting dog. The chest compresses, throwing off the measurement. Always measure standing.
3. Pulling the tape tight. It should rest against the body, not be pulled taut.
4. Sizing down "because they'll grow into it." It's the opposite: for a puppy, size up and choose an adjustable model.

What if my dog is between two sizes?

Go with the larger one, every time. A slightly loose harness can be tightened with the adjustment straps; a too-small harness simply can't be worn.

Which harness type for your needs

• Dog who pulls → an anti-pull harness with a front clip.
• Evening walks → a reflective model.
• Dog who slips out of gear → an escape-proof set.

Not sure? Write to us

Send us your dog's chest girth, neck measurement, and breed: we'll reply with the exact size to order. It's free, and it saves everyone a return. 🐾