How to Measure Your Dog for a Harness (Step-by-Step Guide)
The Short Answer
To measure your dog for a harness, you need two measurements: neck circumference (where a collar sits) and chest (girth) circumference (the widest point of the chest, just behind the front legs). Use a soft flexible tape measure, add one inch of breathing room, and compare against the brand's specific size chart. When in doubt, size up. Straps can be tightened, but a harness that's too small can't be adjusted.
A harness that doesn't fit correctly isn't just uncomfortable. It can chafe, restrict movement, or slip off entirely. The good news: getting the right size is straightforward once you know what to measure and where.
This guide walks you through everything step by step, including the tools you need, the two measurements that matter, how to check fit once the harness is on, and the most common sizing mistakes to avoid.
Prefer to watch? See our step-by-step sizing video →
What You'll Need
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A soft flexible tape measure (the kind used for sewing, not a stiff metal one)
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A helper if your dog won't stand still
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Treats to keep your dog in position
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A pen and paper to record the numbers
If you don't have a flexible tape measure, a piece of string works. Wrap it around the measurement point, mark where it meets, then lay it flat against a ruler.
Step 1: Measure Your Dog's Neck
Stand your dog up on all four legs. Find the base of the neck: the point where a flat collar would naturally sit, just above where the neck meets the shoulders.
Wrap the tape measure around this point snugly but not tightly. You should be able to slip one finger underneath. Note the number.
Why it matters: The neck measurement determines how the harness sits at the top of the chest opening. A neck opening that's too tight will be uncomfortable; too loose and the harness may shift or allow escape.
Step 2: Measure Your Dog's Chest (Girth)
This is your most important measurement. The chest girth is the circumference at the widest part of your dog's ribcage, typically just behind the front legs.
To find the right spot: run your hand along your dog's side from the front leg back until you feel the chest start to widen. That's where you wrap the tape.
Wrap the tape measure all the way around the chest at this point, keeping it level and parallel to the ground. Snug but not compressing the ribs. Note the number.
Add one inch. Unlike clothing, a harness needs a small amount of breathing room beyond the bare measurement. Adding an inch to your chest measurement before checking the size chart gives you the working number.
Why it matters: This is the primary load-bearing measurement on any harness. Most harness brands size entirely by chest girth. If you only take one measurement, take this one.
Step 3: Check the Size Chart
Do not assume sizing is consistent between brands. A "medium" from one brand can be a full size off from another. Always compare your measurements directly against the specific size chart for the harness you're buying.
At Fei and Eve, our size charts list both the neck and chest ranges for each size. Find the row where both your measurements fall. If they land in different size ranges, use the chest measurement as the deciding factor.
If you're between sizes, size up. Adjustable straps can always be tightened down. A harness that's too small cannot be made to fit, and trying to force it creates pressure points and restricts movement.
Step 4: Check the Fit Once the Harness Is On
Measurements get you to the right size. The fit check confirms it. Once you have the harness on your dog, run through this checklist before your first walk:
The two-finger rule. Slide two fingers under every strap: across the chest, around the neck opening, under the belly strap, and along the sides. You should be able to fit two fingers, but not three. If you can fit a whole hand, it's too loose. If you can't fit two fingers, loosen the relevant strap or consider sizing up.
Check the shoulder blades. Ask your dog to take a few steps or watch them walk. The chest strap should sit flat across the breastbone, not pressing against or restricting the shoulder blades. Shoulder restriction affects gait over time and causes discomfort, so this is worth taking a moment to check properly.
Check the armpits. The underarm area is the most common chafing point on any harness. Make sure there's no excess material bunching in the armpit crease. On a well-fitted harness, the strap should sit cleanly without gathering.
Check for escape gaps. Gently push two fingers under the harness at the neck and try sliding it toward your dog's head. If it moves more than an inch or two, it's loose enough that a determined dog could back out of it. This is especially important for dogs that spook easily or resist the harness.
Common Sizing Mistakes to Avoid
Measuring with a stiff tape measure. A rigid tape doesn't contour around the body correctly and gives inaccurate numbers. Always use a flexible tape.
Measuring over a thick coat without accounting for it. If your dog has a particularly dense or fluffy coat, the tape measure will sit above the body surface. For heavily coated breeds, measure snugly through the coat, or measure after a bath when the coat is flat.
Using your old harness size as a reference. Sizes vary between brands and even between product lines within the same brand. Always measure fresh.
Measuring a moving dog. Your dog needs to be standing squarely on all four legs, weight evenly distributed. Sitting or lying down changes the chest shape significantly. Use treats to keep them still.
Skipping the fit check. Measurements get you close. The on-dog check is what confirms it. Don't skip this step, especially for the shoulder and armpit areas.
Measuring for Specific Breeds and Body Types
Deep-chested breeds (Greyhounds, Whippets, Dobermans). These dogs have a large chest-to-waist ratio. Their chest measurement will often put them in a larger size than their body weight suggests. Always go by measurement, not by weight.
Flat-faced breeds (French Bulldogs, English Bulldogs, Pugs). Brachycephalic breeds often have wide chests relative to their neck. Their neck and chest measurements may fall in different size ranges. When this happens, size for the chest.
Golden Retrievers, Doodles, and long-haired breeds. Measure through the coat but err toward the snugger end of the tape. Long fur can compress significantly under a strap, meaning a harness that feels right at fitting can feel loose once the fur settles.
Puppies. Puppies grow fast. If your puppy is in an active growth phase, measure every few weeks and check fit regularly. A harness that fit perfectly at 4 months may be too snug at 6 months. Look for harnesses with wide adjustment ranges.
FAQ
How do I measure my dog for a harness?
You need two measurements: neck circumference (where a collar sits) and chest girth (the widest point of the chest, just behind the front legs). Use a flexible tape measure, add one inch to the chest measurement for breathing room, and compare to the brand's size chart.
What is the most important measurement for a dog harness?
Chest girth. This is the primary sizing measurement for almost all harness brands. If you can only take one measurement, take the chest: just behind the front legs at the widest point of the ribcage.
How tight should a dog harness be?
The two-finger rule: you should be able to slide two fingers comfortably under any strap, but not three. The harness should not restrict the shoulder blades during movement, and there should be no excess material bunching in the armpits.
What if my dog is between harness sizes?
Size up. Adjustable straps can be tightened to fit a smaller measurement range. A harness that's too small cannot be made to fit and will cause pressure points and discomfort.
How do I measure a puppy for a harness?
The same way: neck and chest measurements with a flexible tape. Just keep in mind that puppies grow quickly. Check fit regularly and look for harnesses with wide strap adjustment ranges to extend the life of the harness through growth phases.
Why does my dog's harness fit differently after a bath?
Long or dense coats can hold volume that compresses when wet. If the harness feels looser after bathing, it's likely because the coat is lying flatter against the body. Check and readjust straps once dry.
Can I use my dog's weight to pick a harness size?
Weight is a rough guide at best. Body shape varies significantly between breeds. A 40-pound Greyhound and a 40-pound Bulldog have completely different chest proportions. Always measure; never size by weight alone.
What It Comes Down To
Getting the right harness size comes down to two measurements, one size chart, and a fit check once it's on. Take five minutes to do it right the first time and you'll avoid the frustration of a return and, more importantly, you'll have a harness your dog can actually wear comfortably.
If you're still unsure after measuring, the [Find Your Harness Quiz →] walks you through five quick questions and recommends the right Fei and Eve harness for your dog's size, breed, and walking style.
Shop the Classic Harness →
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