How to Measure Your Dog for a Harness or Collar

A collar or harness that's too loose lets your dog slip out of it. Too tight, and it rubs, chafes, or restricts movement. The sizing chart on a product page only works if you know how to take the measurement it's asking for, and that's where most people go wrong. They guess based on weight or breed, order the wrong size, and end up measuring anyway after the fact.

This guide walks through exactly how to measure your dog for three of the most common pieces of gear: a Roman-style harness, a martingale collar, and a buckle collar. Grab a soft measuring tape (the kind used for sewing, not a metal one) before you start. If you don't have one, a piece of string works too. Just measure the string against a ruler afterward.

The Two-Finger Rule

Before you get into product-specific steps, one rule applies across all three: once the gear is on, you should be able to slide two fingers flat between it and your dog's body. Any tighter and it's restricting movement or breathing. Any looser and your dog can back out of it. Keep this in mind as you measure and again once the piece is on.

How to Measure for a Roman-Style Harness

A Roman harness (we build ours as the Escape Free Dog Harness) sits differently than a collar. Instead of one neck measurement, you need the girth, which is the circumference around the widest part of your dog's ribcage, right behind the front legs. This is the measurement that determines whether your dog can back out of the harness or not, so it's worth taking twice to confirm.

Steps:

1. Stand your dog on all fours on a flat surface. Don't measure while they're sitting or lying down, the girth changes.
2. Find the widest part of the ribcage, just behind the front legs.
3. Wrap the tape snugly around that point, all the way around the body.
4. Note the measurement, then check it against two fingers of slack. Adjust if needed.
5. Compare the number to our harness sizing chart to find your size.

If your dog is between sizes, or you expect coat growth or weight change, size up rather than down. A slightly loose harness can be tightened at the adjustable straps. An undersized one can't be let out past its max.

Explore the Roman Harness collection.

How to Measure for a Martingale Collar

A martingale is a training collar. It tightens slightly when your dog pulls, which prevents backing out of it, but it's not meant to be worn full time since it doesn't have a quick-release buckle. The measurement you need here is neck circumference, taken at the specific spot a collar naturally sits.

Steps:

1. With your dog standing, find the base of the neck, just above the shoulders, where a collar would naturally rest.
2. Wrap the tape around that point. Keep it snug but not pulled tight.
3. Record the measurement.
4. Because a martingale is designed to have some give for the tightening action, check our collar sizing chart rather than assuming a 1:1 fit with a buckle collar. Martingale sizing runs differently since the collar needs room to close.

If your dog has a thick or double coat, part the fur down to the skin before measuring so you're not adding extra inches from fluff.

Explore the Martingale Collar collection.

How to Measure for a Buckle Collar

A buckle collar is the everyday, all-day option, so getting the fit right matters more here than anywhere else since your dog will likely wear it constantly. Same neck measurement as the martingale, but because a buckle collar doesn't tighten on its own, the fit needs to be right from the start.

Steps:

1. Stand your dog and locate the base of the neck, just above the shoulders.
2. Wrap the tape snugly around that point, not the tightest part of the neck lower down.
3. Slide two fingers flat under the tape to confirm there's room without excess slack.
4. Record the measurement and compare it to our collar sizing chart.

Buckle collars come in fixed lengths with some adjustment range built in through the holes or slider, so if your dog's measurement falls between two sizes, check the adjustment range listed on the product page rather than the midpoint size alone.

Explore the Buckle Collar collection.

A Few Things That Throw Off a Measurement

• Measuring while your dog is sitting or lying down instead of standing
• Pulling the tape too tight, which shrinks the number and gives you a collar or harness that's actually too small
• Not accounting for a thick coat that gets clipped or brushed out seasonally
• Measuring a growing puppy once and not rechecking a few months later

Still Unsure of the Size?

Send us your dog's measurements and current weight at hello@luwello.com and we'll help you pick the right size before you order.