The 30-second version
- Use a soft tape measure in centimetres, with your dog standing square on a level floor.
- Chest girth (for harnesses and coats): around the widest part of the ribcage, just behind the front legs1.
- Neck: around the base of the neck, at its lowest point1.
- Back length (for coats): from the base of the neck to the base of the tail.
- Keep the tape flat and snug, not tight. Measure twice1.
What you need
- A soft tailor's tape measure. No tape? Use a long piece of string, mark it, and measure the string against a ruler or metal tape afterwards1.
- Small, tasty treats, to keep your dog standing still and happy.
- A helper if you can. One person holds and treats, the other measures.
- Bathroom scales for weighing (or your vet practice's scales for a big dog).
- Something to write on, or the [measurement record](#record) at the bottom of this page.
Getting your dog ready
- Pick a calm moment, such as after a walk, not when your dog is excited to go out.
- Take off any harness, coat or bulky collar. They change the reading.
- Stand your dog on a level, non-slip floor with all four feet squarely underneath it and the head up in a natural position. A sitting or lying dog's chest, back and coat change shape and give the wrong numbers.
- Keep sessions short. Measure one thing, give a treat, then do the next.
- If your dog is worried about being touched or about the tape, stop. Show the tape, treat; touch it to the dog's side, treat; build up over a few days. A rushed, wriggling measurement is usually wrong anyway.
Chest girth: the one that matters most
Chest girth (the distance around the body) decides the size of almost every harness and most dog coats. Get this one right and you've done most of the work.
- Find the spot: the widest part of the ribcage, just behind the front legs1. Run your hand back from the elbow and you'll feel the ribs widen out.
- Pass the tape under the chest and bring both ends up to meet on top of the back.
- Check the tape is straight and level all the way round, not slanting back towards the waist, and not twisted.
- Pull it snug so it sits against the body without squeezing: snug, "without being too tight or baggy", as Julius-K9 puts it2. On a fluffy dog, push the tape through the coat to the body.
- Read the number where the end of the tape meets the rest of it. Write it down in centimetres.
- Measure again. If the two readings differ, use the larger one.
Where each brand measures the chest
| Brand | Measuring point |
|---|---|
| Julius-K9 | A set distance behind the front legs that depends on the size: two finger-widths for Baby 1 and 2, three for Mini-Mini and Mini, four for size 0 and up. Measure at the finger furthest from the legs2. |
| Ruffwear | Around the widest part of the chest, just behind the front legs1. |
| Other brands | Most use the widest part of the chest behind the front legs. Always read the brand's own measuring note, because a few measure somewhere else. |
Neck
- Measure around the base of the neck, at its lowest point, where it meets the shoulders1. That is where the neck strap of a harness sits.
- For a collar, measure a little higher up, where the collar will sit. Check the brand's chart to see whether it wants the neck size exactly or has already added room.
- Overhead harnesses must also go over the head. If your dog has a broad head (bull breeds, for example), check that the neck opening at its largest will pass over it.
Back length
You'll need this for dog coats, and it helps check whether a vest-style harness suits a long-backed dog.
- Measure along the spine from the base of the neck, where a collar sits, to the base of the tail, where the tail joins the body. Don't include the tail.
- Keep your dog's head up and straight. A dog looking down or round at you stretches or shortens its back.
- Coat makers don't all measure back length the same way. Some measure to the base of the tail, some to where the coat should end. Check the chart before you compare.
Height at the shoulder
Used for crates, some beds and car crates.
- Stand your dog next to a wall on a level floor.
- Find the withers: the highest point of the shoulder blades, just behind the neck.
- Lay a book or ruler flat across the withers so it touches the wall, and mark the wall where its underside meets it.
- Measure from the floor to the mark.
Nose-to-tail length
- With your dog standing, measure in a straight line from the tip of the nose to the base of the tail.
- Crate and bed guides usually add extra space to this so your dog can turn and stretch out. We'll cover that in our crate and bed guides, so for now just record the measurement.
Weight
Some brands give weight ranges as a second guide, and weight helps you track a growing puppy.
- Weigh yourself on bathroom scales. Then weigh yourself holding your dog. Take the first number from the second.
- For a dog too big to lift, ask your vet practice: many let you pop in and use their scales.
- For a small puppy, place a box or basket on kitchen scales, zero it, and put the puppy in.
- Weigh at about the same time of day each time, ideally before a meal, so readings are comparable.
Inches and pounds
UK and European brands mostly use centimetres and kilograms. If your tape or scales use imperial units, convert first: inches × 2.54 = centimetres and pounds × 0.4536 = kilograms.
= – cm
= – kg
Puppies, fluffy dogs and other special cases
Puppies
Size a puppy on its measurements today, not on what you expect it to reach1. Research on millions of pet dogs shows small breeds reach adult weight sooner than large ones, and large breeds can keep growing into their second year3.
We suggest measuring the chest every two weeks while your puppy is growing fast, then monthly until the numbers stop changing. If you can no longer slide two fingers under the harness straps, measure again.
Fluffy and double-coated dogs
Press the tape through the coat until it sits against the body. A tape resting on the fluff can read several centimetres too big.
Measure again after grooming or clipping, and adjust the harness: less coat means a looser fit. Our Cockapoo and Golden Retriever guides go into more detail.
Deep-chested and barrel-chested dogs
Dogs such as Staffies, French Bulldogs and Labradors have a chest that is big for their weight. Always size these breeds by chest girth, not weight. See our Staffordshire Bull Terrier guide for an example.
Flat-faced (brachycephalic) dogs
Keep the tape and any strap well clear of the throat. The RSPCA advises walking flat-faced dogs on a harness rather than a collar to avoid pressure on the neck4.
Long-backed dogs
Measure the chest level with the ground, not at a slant, and take the back length too so you can check vest-style harnesses aren't too short. See our Dachshund guide.
Wriggly dogs
Use string: loop it round, pinch the point where it meets, and measure the string afterwards1. It's quicker than reading a tape on a moving dog. A helper feeding treats at nose height keeps most dogs standing.
Older or stiff dogs
Measure in short goes and let your dog rest in between. If standing seems uncomfortable for your dog, check with your vet.
Common measuring mistakes
| Mistake | What happens | Fix |
|---|---|---|
| Measuring the neck for a harness | The harness is too small around the body | Harness sizes go by chest girth |
| Tape resting on top of a fluffy coat | A size too big; it slips | Push the tape through the coat to the body |
| Tape pulled tight | A size too small; it rubs | Snug, flat, not squeezing |
| Tape slanting back towards the waist | Reading too small | Keep the tape level, just behind the front legs |
| Measuring a sitting or lying dog | Wrong chest and back readings | Measure standing square |
| Measuring in inches, reading a chart in cm | Wildly wrong size | Convert: inches × 2.54 = cm |
| Going by weight alone | Wrong size for deep-chested breeds | Use weight only as a tie-breaker |
| Using last season's measurements for a puppy | Too small | Re-measure before every purchase |
From numbers to the right size
- Compare your dog's chest in centimetres with each brand's chart, not the size letters. A Medium in one brand can be a Large in another.
- Brand charts often overlap, so your dog may fit two sizes. Choose the size where your measurement sits nearer the middle, so the harness can adjust either way.
- If your dog is fully grown and right on the border between two sizes, Ruffwear recommends choosing the larger size5.
- Julius-K9 gives weight ranges as well as chest ranges; use weight to decide between two sizes that both fit the chest2.
- Or let our size finder do it: pick the breed, enter the chest and weight, and it shows the size in each brand.
Harness guides by breed
- Border CollieHarness size guide
- CockapooHarness size guide
- Cocker SpanielHarness size guide
- French BulldogHarness size guide
- Golden RetrieverHarness size guide
- Labrador RetrieverHarness size guide
- Staffordshire Bull TerrierHarness size guide
- Standard DachshundHarness size guide
Checking the fit when it arrives
- You should be able to slide two fingers flat under every strap, and no more5.
- The strap around the body sits a little way behind the front legs, not pressed into the "armpit".
- Nothing presses on the throat.
- Your dog's stride looks the same with and without the harness. A small study found harnesses can shorten how far the shoulder reaches forward6.
- After the first few walks, check behind the front legs and under the chest for redness or rubbed fur. If the skin is sore, stop using the harness and ask your vet.
Measurement record
Print this page or copy the table to keep track, especially for a growing puppy.
| Date | Chest (cm) | Neck (cm) | Back (cm) | Height (cm) | Weight (kg) |
|---|---|---|---|---|---|
Questions about measuring
Where exactly do I measure my dog for a harness?
Should the tape be tight or loose?
Snug against the body, flat and untwisted, but not squeezing: "without being too tight or baggy"2. On a fluffy dog, push the tape through the coat to the body.
Can I measure my dog with string?
Yes. Wrap the string round, pinch where it meets, then measure the string against a ruler or tape1.
How do I convert inches to centimetres?
Multiply inches by 2.54. For pounds to kilograms, multiply by 0.4536. Or use the converter on this page.
How often should I measure my puppy?
We suggest every two weeks while it is growing fast, then monthly until the measurements stop changing. Always buy for its size today1.
Is weight or chest size more important for a harness?
Chest girth. Weight is only a rough guide because dogs of the same weight can have very different chests. Use weight as a tie-breaker when the chest fits two sizes2.
My dog won't stand still. What can I do?
Measure after a walk, use a helper with treats at nose height, and try the string method. Keep sessions short and stop if your dog is worried.
Why is my dog a different size in different brands?
Each brand designs its own sizes and chest ranges, and many overlap. Always compare your dog's measurement in centimetres against each chart.