How to Measure a Dog for a Harness

Quick answer Measure the widest part of the chest just behind the front legs, and the neck where a collar sits, with a soft tape or string, then compare both numbers with the maker's own size chart. If between sizes, choose the larger and adjust the straps. A correctly fitted strap lets two fingers slide underneath.

A harness that is too loose can slip, and one that is too tight can rub and restrict movement, so sizing matters more than most people expect. The good news is that the method is simple and needs no special tools. This guide shows exactly where to measure, how to record the numbers, how to read a maker’s size chart, what to do if your dog is between sizes and how to check the fit once the harness is on.

What you need

A soft measuring tape, or a piece of string and a ruler.
A treat or two, and a calm moment.
A notebook or phone to write down the numbers in both centimetres and inches.

If your tape is in inches and the chart is in centimetres, or the other way round, the Pet Measurement Converter converts exactly (1 in = 2.54 cm).

Measurement 1: chest girth

Chest girth is the main number on almost every harness chart.

Have your dog stand on level ground, relaxed, with its head up.
Find the widest part of the chest, just behind the front legs, where the chest is deepest.
Wrap the tape around the whole chest, over the back, and under the belly. Keep it level, not twisted.
Make the tape snug but not tight: flat against the coat, with no gaps, but without squeezing.
Read where the tape meets. Write it down.

If you use string, mark where it overlaps, then lay it flat and measure against a ruler.

Measurement 2: neck

Some harnesses use the neck as well, especially those with a neck loop.

Find the point where a collar usually sits, at the base of the neck.
Wrap the tape around, snug, and check that two fingers can slide under it.
Write down the number. For measurements around a neck with a lot of loose skin or fur, take the number with the tape lying flat.

Measurement 3 (if asked): back length

A few makers ask for back length, from the base of the neck to the base of the tail. If the chart asks for it, measure along the spine with the dog standing.

Reading the maker’s size chart

A chart gives a range of chest girth for each size, and sometimes a neck range as well. Find your dog’s chest number in the ranges and choose the size whose range contains it, then check that the neck number also falls inside that size’s neck range. If the two numbers point to different sizes, read the maker’s notes: some brands size by chest and treat the neck as adjustable, and others do the reverse.

Real charts differ between brands and between models of the same brand, so never reuse one brand’s ranges for another. Our harness size chart guide explains how to compare charts.

If your dog is between sizes

When the chest girth falls near a boundary, or the chest and neck suggest different sizes, the usual advice is to choose the larger size and tighten the straps. A harness with plenty of adjustment is more forgiving than a fixed-size one. If your dog is still growing or may lose weight, an adjustable design is more practical. Try the harness on before buying if you can, and check the shop’s return policy.

The fit check

Once the harness is on:

Two-finger test. You should be able to slide two fingers under every strap, but not much more.
No gaps or rubbing. Look at the armpits and neck for chafing or pinching.
Free movement. Watch your dog walk and trot; the harness should not restrict the shoulders.
No slipping. Gently pull on the lead; the harness should not rotate or ride up.
Comfortable. The dog should walk normally rather than freeze or shuffle.

Check again after a few outings, since straps loosen and the dog’s coat compresses.

A worked example

A dog’s chest, measured twice, comes to 70 cm (27.6 in) and the neck to 40 cm (15.7 in).

Write down both numbers in both units.
On the maker’s chart, 70 cm sits exactly on the boundary between the medium and large chest ranges.
The dog is between sizes, so the owner picks the large and tightens the straps.
The two-finger test passes on all straps and the dog walks normally.
The owner makes a note to re-measure in a month, since the dog is young.

Puppies and growing dogs

A puppy changes size every few weeks. Choose an adjustable harness and measure every two to four weeks, or whenever the straps are at the end of their range. Use the Dog Crate Size Calculator with the same measuring habit for a crate; the two sets of numbers help you plan gear as the puppy grows.

Dogs with unusual shapes

Deep-chested dogs may need a longer chest strap or a model designed for them.
Very short-legged dogs may need a harness with a low neckline.
Thick-coated dogs need a fit check over the coat.
Dogs with a narrow waist may slip out of a loose harness.
Dogs with neck or back problems: ask your vet about suitable designs.

Common mistakes

Measuring the neck only.
Taking the tape too loose or too tight.
Assuming “medium” is the same everywhere.
Skipping the fit check.
Never re-measuring a growing dog.
Choosing a size so large that the harness shifts.

Questions to ask the seller or your vet

Which size does the maker’s chart suggest for these measurements?
How much adjustment does the harness have?
Is there a returns policy if it does not fit?
Is this design suitable for my dog’s shape and activity?
Do I need a different style for a medical reason?

Measuring different kinds of dog

The method is the same for every dog, but a few shapes need extra thought.

Dog	What to watch	Tip
Deep-chested (such as a sighthound)	The chest is much deeper than it is wide, and the narrow waist can let a harness slip back	Measure at the deepest point and check the strap behind the front legs
Barrel-chested and short-legged	The chest may be nearly as wide as the dog is long	Take the girth twice, and check the harness does not press on the belly
Long-coated	The coat adds bulk and hides the shape	Compress the coat lightly, and confirm the fit by hand
Thick-necked	Over-the-head designs may not clear the neck	Check the neck opening or choose a step-in design
Very small	Even a centimetre matters	Use a soft tape and measure twice
Very large	The tape may not be long enough	Use a long tape or string, and ask for help

Whatever the dog, the same rule applies: record the numbers and compare them with the maker’s chart.

Getting a nervous dog to stand still

Some dogs dislike being measured. A few tricks help:

Do it after a walk, when the dog is calm.
Give a treat for standing still, and break the job into short steps.
Use a string so that nothing cold or crinkly touches the dog, then measure the string.
Ask a second person to hold the dog’s attention with a treat or a toy.
Stop and try again later if the dog is stressed.

Count the treats in the day’s allowance. A dog that is taught to enjoy measuring will be easier at every vet visit and fitting session.

A measuring card to keep

Measurement	cm	in	Date
Chest girth (widest)
Neck (collar position)
Back length (neck base to tail base)
Height (floor to withers)
Weight

Keep it in your phone or on the fridge. If a puppy is growing, add a new line every few weeks. It also helps when ordering a coat, a crate or a bed, as in our dog crate size chart guide.

Trying on and testing

Once the harness arrives:

Put it on in the house first, with treats, so the dog links it with something pleasant.
Adjust the straps one at a time, checking the two-finger rule.
Walk around the room and watch for rubbing, restriction or odd movement.
Take a short walk outside, and check again afterwards for hot spots or marks.
Adjust, and try a longer walk the next day.

If the dog hates it, do not force it: go back a step, use more treats and shorter sessions, or ask a trainer.

Measuring step by step again, with a checklist

Use a soft tape on a calm dog standing on level ground.

Find the widest part of the chest, just behind the front legs.
Wrap the tape around, snug but not tight, with two fingers’ room.
Note the figure in centimetres and inches.
Measure the neck where a collar would sit.
Measure again to check.
Compare with the maker’s chart, which may be different from another brand’s.

If the dog is between sizes, many owners choose the larger one with adjustable straps. The Dog Harness Size Calculator converts the chest figure to a size band.

Tips for a wriggly dog

Use treats to keep the dog still.
Ask a helper to hold the dog’s attention.
Use a piece of string, then lay it against a ruler.
Measure after a walk when the dog is calm.

Recording and rechecking

Write the date and measurements, and re-measure after weight changes or every few months for a growing dog. See harness vs collar for which to choose.

Special body shapes

Deep-chested dogs have a chest much larger than the waist, so a harness must clear the chest but not hang loose at the belly. Barrel-chested short-legged dogs often sit between sizes, and an adjustable harness with several straps helps. Fluffy coats hide the true size, so feel the body through the coat and measure over the skin line rather than the fur. If measurements fall into two sizes, ask the maker or a shop with a fitting service.

Quick summary

Measure the chest at its widest point behind the front legs, and the neck where a collar sits.
Compare both numbers with the maker’s own chart; there is no universal standard.
If between sizes, choose the larger and tighten the straps.
Check the fit: two fingers under every strap, no rubbing, no slipping.
Re-measure a growing dog every few weeks.
Use the Dog Harness Size Calculator to record your dog’s numbers.

Frequently asked questions

How do I measure my dog for a harness?

Measure chest girth at its widest part behind the front legs, and the neck at the base where a collar sits, using a soft tape or a piece of string and a ruler.

Do harness sizes match between brands?

No. There is no universal standard, so always use the maker's size chart with your dog's own measurements.

What if my dog is between two sizes?

Choose the larger size and tighten the straps, and check the fit again.

How tight should a harness be?

You should be able to slide two fingers under every strap, and the dog should move freely without the harness shifting or rubbing.

Should I measure over fur?

Measure snugly with the coat lightly pressed, not stretched, and check the fit with the harness on.

How often should I re-measure?

For a puppy, every few weeks. For an adult, when weight changes by a few kilograms or when you change harness type.

Do I need the length of the back?

Some makers ask for it. Check the chart for each model.

Sources

Manufacturer sizing guidance (general industry convention; harness sizes are not standardised between brands)
AKC expert advice (owner guidance; practical rule of thumb)

Reviewed by the CalcuPaw Veterinary Review Team

Last reviewed 18 Oct 2026 · Meet the review team · This guide is general information, not veterinary advice.