How to Measure Your Dog for a Collar or Harness That Actually Fits

A collar that's too loose slips over the ears. A harness that's too tight rubs them raw. Getting the fit right is the single most important thing you can do before you buy — for their comfort, their safety, and so the piece you choose actually lasts. Here's how we measure our own dogs.

Why fit matters more than size

"Small, medium, large" means something different at every brand. A medium harness from one maker can sit completely differently from another's. That's why we never ask you to guess from a label — we ask for two numbers: the neck and the chest. Get those right and everything else follows.

What you'll need

A soft tape measure works best — the kind used for sewing. No tape? A piece of string and a ruler will do the job just as well. Measure when your dog is calm and standing naturally, not sitting or lying down.

Measuring the neck (for collars)

1. Wrap the tape around the base of the neck, where a collar would naturally sit — low, just above the shoulders.
2. Keep it snug but not tight.
3. Slide two fingers between the tape and their neck. That's the room you want to leave for everyday comfort.

Write the number down. If they're between two sizes, size up — you can always tighten a collar, but you can't add length.

Measuring the chest (for harnesses)

1. Find the widest part of the ribcage, just behind the front legs.
2. Wrap the tape all the way around and note where it meets.
3. Again, leave two fingers of room.

The chest measurement is what carries the load on a walk, so it matters most for a harness that sits comfortably and doesn't shift.

A quick size reference

Use your own numbers as the guide — breeds are only a rough starting point:

• XS · 25–35 cm · under 5 kg · Chihuahua, Yorkie
• S · 30–40 cm · 5–10 kg · Mini Dachshund, Pomeranian
• M · 38–48 cm · 10–18 kg · Beagle, Cocker Spaniel
• L · 45–55 cm · 18–30 kg · Labrador, Border Collie
• XL · 53–65 cm · 30 kg+ · German Shepherd, Ridgeback

Three mistakes we see most often

Measuring over a thick coat. If your dog has a heavy double coat, measure against the body and add a little room — or size up.

Measuring a puppy for the year ahead. Puppies grow fast. Measure for now, not for later; a collar that fits today is safer than one they'll "grow into."

Forgetting the two-finger rule. Too loose and it slips; too tight and it rubs. Two fingers is the sweet spot, every time.

Still not sure?

Send us your dog's measurements — or just a photo and their breed — and we'll help you choose. Every Forevervow piece is made to be worn for years, and that starts with getting the fit right from day one. Talk to us here.