How to measure your dog for a harness, collar and coat

6 October 2026 · 2 min read · By FELL

Most sizing problems come from guessing. A soft tape measure and two minutes fixes that. You need four numbers: neck, chest, back length and weight.

What you need

A soft tape measure (a piece of string and a ruler works too)
Your dog standing up, not sitting or lying down
A treat, for the patience

1. Neck

Measure around the neck where a collar naturally sits, about halfway between the ears and the shoulders. Keep the tape snug but not tight — you should be able to slide two fingers flat under it. This is the number you need for a collar, and the neck strap of a harness.

2. Chest

Measure around the widest part of the ribcage, just behind the front legs. This is the most important number for a harness and for a coat, because it's where both have to fit without rubbing or sliding round.

3. Back length

Measure along the spine from the base of the neck (where the collar sits) to the base of the tail. Coats and rain capes are sized mainly on this — too short leaves the back wet, too long gets in the way when your dog squats.

4. Weight

Weight isn't used on its own, but it's a useful check: if the tape says one size and the weight says another, measure again.

Comparing with the size guide

Every FELL product that comes in sizes has a size guide on its page. Match your measurements to the chart, starting with the most important one for that product:

Collar: neck
Harness: chest first, then neck
Winter coat and rain cape: back length first, then chest
Beds and mats: your dog's length from nose to base of tail when stretched out, plus a little room

If your dog is between sizes

For coats, capes and harnesses, the larger size is usually the safer choice — adjustable straps take up the slack, but nothing can add length that isn't there. For collars, check where your dog's neck sits in each size's adjustment range and pick the one that puts it nearer the middle.

Still not sure? Email support@fell.pet with your dog's breed, weight and the measurements above, and we'll tell you which size to order. And if it arrives and doesn't fit, you have 30 days to send it back.