Wrong-sized harnesses are one of the most common pet product returns — and one of the most preventable. A harness that's too loose lets your dog slip out mid-walk (it happens faster than you'd think). One that's too tight causes chafing, restricts breathing, and makes your dog reluctant to wear it.

The good news: measuring your dog for a harness takes about 60 seconds and requires nothing more than a fabric tape measure. Here's exactly how to do it.

The Two Measurements That Matter

Most harness sizing is based on two measurements: chest girth and neck girth. Of the two, chest girth is by far the more important — it's the measurement most harnesses are primarily sized by, and it's where fit problems usually originate.

Chest Girth (Most Important)

This is the circumference of the widest part of your dog's ribcage — usually just behind the front legs.

How to measure:

1. Stand your dog on a flat surface
2. Find the widest point of their chest (roughly where their front legs meet their body)
3. Wrap the tape measure around the full circumference at that point
4. Pull it snug but not tight — you should be able to slip two fingers underneath
5. Note the measurement in centimetres

Pro tip: If your dog is wriggly, do this right after a walk when they're calmer.

Neck Girth (Secondary)

This is the circumference of your dog's neck where the harness collar sits — typically at the base of the neck, not the throat.

How to measure:

1. Find the base of your dog's neck, just above where the shoulders begin
2. Wrap the tape measure around at that point
3. Again, two-finger rule applies

Back Length (For Jacket-Style Harnesses)

Some harnesses — particularly tactical or vest-style ones — also use back length. Measure from the base of the neck (where the collar sits) to the base of the tail.

Harness Size Charts by Breed

Different harness styles size differently, but here are the typical ranges for common breeds. Always check the specific product's size chart before ordering.

The Two-Finger Rule

Regardless of what size you order, always apply the two-finger rule when fitting:

• Slide two fingers under any strap
• If you can't fit two fingers, it's too tight
• If you can fit a whole hand, it's too loose

The two-finger test applies to chest straps, belly straps, and neck openings separately.

Common Fitting Problems (and How to Fix Them)

The harness spins sideways Usually means the belly strap is too loose. Tighten the belly band first, then readjust the chest strap.

Your dog keeps slipping out the front The neck opening is too large. If your harness has an adjustable neck strap, tighten it. If not, you need a smaller size.

Your dog's front legs keep getting caught The chest plate is sitting too far back. Move it forward so it sits flat across the chest, not over the legs.

Chafing under the armpits The belly strap is rubbing in the wrong position. It should sit just behind the front legs, not on them. Try repositioning before assuming the size is wrong.

Dog actively resists being harnessed Usually a negative association from past tight fitting. Do several short positive sessions where you touch the harness, feed a treat, put it on briefly, feed more treats. Most dogs come around within a week.

Front-Clip vs Back-Clip: Which Should You Choose?

Back-clip harness

• Leash attaches at the back between the shoulder blades
• Best for: calm walkers, dogs who don't pull, small breeds, puppies still in training
• Limitation: can actually encourage pulling in strong dogs (the natural opposition reflex)

Front-clip harness

• Leash attaches at the chest
• Best for: pullers, dogs in no-pull training, medium to large breeds
• How it works: clips at the chest redirect the dog sideways when they surge forward, breaking the pulling motion naturally

Dual-clip harness

• Has both front and back rings
• Best for: training in progress (use front clip until pulling stops, then switch to back)
• Most versatile option for everyday use

Our Adjustable No-Pull Tactical Harness has both front and back D-rings, padded chest panel, and full size chart from S to XL.

What If Your Dog Is Between Sizes?

If your dog's chest measurement falls between two sizes, here's the rule:

• Deep-chested breeds (French Bulldog, Boxer, Rottweiler): size up
• Narrow-chested breeds (Greyhound, Whippet, Collie): size down
• For vest-style harnesses with back length: use the chest measurement as the primary guide, not the back length

Measuring Puppies

Puppies grow fast. If your puppy is under 6 months, buy a harness with the widest adjustment range possible — you'll save money on re-buying as they grow. Measure every 4–6 weeks during peak growth stages (typically 2–6 months for small breeds, 3–10 months for large breeds).

Ready to find the right harness? Browse our full range at petivoo.store with free shipping on orders over $50 and 30-day returns if the fit isn't right.