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Quick answer
An adult French Bulldog usually measures 45–65 cm around the chest and weighs 8–13 kg1.
These are the sizes most adult French Bulldogs need. Your dog may differ, so measure to be sure.
Get an exact size for your dogHow a French Bulldog is built, and why it matters for fit
Breed standards describe the French Bulldog as compact, deep and broad through the chest, with well-sprung ribs that make a barrel-shaped ribcage2. The chest is wide and heavy compared with a narrower waist behind it.
That shape has two effects. The chest measurement is large for such a short dog, so size by chest girth, not by height or weight. And because the waist is narrower than the chest, a loose harness can slide backwards and a Frenchie can reverse out of it.
French Bulldogs are brachycephalic (flat-faced). The RSPCA advises walking flat-faced dogs on a harness rather than a collar, to avoid putting pressure on the neck and to help them breathe more easily3. Flat-faced dogs can also struggle in the heat3, which affects the kind of harness you choose.
How to measure your French Bulldog, step by step
- Get a soft tape measure, or a piece of string and a ruler. Stand your dog on a level floor with all four feet square underneath it.
- Find the measuring point: the widest part of the ribcage, just behind the front legs4. Julius-K9 asks you to measure a set distance behind the front legs, which depends on the size: two finger-widths for the Baby sizes, three for Mini-Mini and Mini, and four for size 0 and up5.
- Wrap the tape all the way round. Keep it flat and untwisted, snug against the body but not squeezing. Read the number in centimetres where the end meets the tape.
- Measure twice4. If the two readings differ, use the larger one.
- Weigh your dog too. Julius-K9 gives a weight range for every size as a second guide5; the other brands here size by chest only.
French Bulldog measuring tips
- Measure around the widest part of the barrel, just behind the front legs. On a Frenchie this is well forward, close to the legs.
- Frenchies have a short coat, so keep the tape flat and snug.
- Also measure the neck at its base. On a flat-faced dog the neck strap must sit low, well clear of the throat.
Want every detail, including neck, back length and weighing at home? Read our complete guide to measuring your dog.
French Bulldog harness size by brand
Each brand cuts its sizes differently, so the same dog can be a different size, or a different letter, in each. Here is how a typical adult French Bulldog fits each chart, and why.
Julius-K9
IDC Powerharness
Julius-K9 lists a chest range and a weight range for every size5. Chest girth is the main guide; we use weight to choose between two sizes when the chest fits both.
- A smaller French Bulldog (chest 45 cm, 8 kg): size Mini-Mini (also fits Baby 2)
- A typical French Bulldog (chest 55 cm, 10.5 kg): size Mini
- A larger French Bulldog (chest 65 cm, 13 kg): size Mini (also fits 0, 1)
Overlaps in the French Bulldog range: 49–53 cm: sizes Mini-Mini and Mini both fit; 58–65 cm: sizes Mini and 0 both fit; 63–65 cm: sizes 0 and 1 both fit.
Sizes overlap by design; chest girth is the main guide, weight is secondary.
| Size | Chest | Weight |
|---|---|---|
| Baby 1 | 29–36 cm | 0.8–3 kg |
| Baby 2 | 33–45 cm | 2–5 kg |
| Mini-Mini | 40–53 cm | 4–7 kg |
| Mini | 49–67 cm | 7–15 kg |
| 0 | 58–76 cm | 14–25 kg |
| 1 | 63–85 cm | 23–30 kg |
| 2 | 71–96 cm | 28–40 kg |
| 3 | 82–115 cm | 40–70 kg |
| 4 | 96–138 cm | 70–90 kg |
Highlighted rows are the sizes typical adult French Bulldogs need.
Check price on AmazonRuffwear
Front Range Harness
Ruffwear sizes the Front Range Harness by chest girth only6, so your tape measure is all you need.
- A smaller French Bulldog (chest 45 cm): size XS
- A typical French Bulldog (chest 55 cm): size XS
- A larger French Bulldog (chest 65 cm): size S
Sized by chest girth only.
| Size | Chest |
|---|---|
| XXS | 33–43 cm |
| XS | 43–56 cm |
| S | 56–69 cm |
| M | 69–81 cm |
| L/XL | 81–107 cm |
Highlighted rows are the sizes typical adult French Bulldogs need.
Check price on AmazonBailey & Coco
Trail & Glow Harness
Bailey & Coco sizes the Trail & Glow Harness by chest girth only7, so your tape measure is all you need.
- A smaller French Bulldog (chest 45 cm): size S (also fits XS, M)
- A typical French Bulldog (chest 55 cm): size M (also fits S, L)
- A larger French Bulldog (chest 65 cm): size L (also fits S, M)
Overlaps in the French Bulldog range: 45–50 cm: sizes XS and S both fit; 45–65 cm: sizes S and M both fit; 55–65 cm: sizes M and L both fit.
Very adjustable, so neighbouring sizes overlap a lot. Sized by chest girth only.
| Size | Chest |
|---|---|
| XXS | 22–41 cm |
| XS | 26–50 cm |
| S | 35–66 cm |
| M | 40–71 cm |
| L | 55–83 cm |
| XL | 71–99 cm |
Highlighted rows are the sizes typical adult French Bulldogs need.
Check price on AmazonPuppies and growing dogs: when to re-measure
French Bulldogs are small to medium dogs, and smaller dogs reach their adult weight sooner than large breeds8. A Frenchie's chest keeps broadening as it matures, so keep measuring, and re-check if its weight changes.
The largest study of puppy growth so far, based on records from over 6 million young dogs, grouped dogs by adult weight: under 6.5 kg, 6.5–9, 9–15, 15–30 and 30–40 kg8. An adult French Bulldog at 8–13 kg falls in the 6.5–9 kg and 9–15 kg groups.
Size a puppy on its chest measurement today, not on the size you expect it to reach4. A harness bought to "grow into" is loose now, and a loose harness slips, rubs and is easier to back out of.
While your puppy is growing fast, we suggest measuring its chest every two weeks, then monthly until it stops changing. A quick check in between: if you can no longer slide two fingers under the straps, measure again.
Most harnesses adjust over a good part of their range, so a growing puppy may stay in one size for a while. When your puppy's chest reaches the top of its size's range, move up.
If your French Bulldog is between two sizes
Brand charts often overlap, so a chest measurement can fall inside two sizes. Here is where that happens for a typical adult French Bulldog:
- Julius-K9: 49–53 cm: sizes Mini-Mini and Mini both fit; 58–65 cm: sizes Mini and 0 both fit; 63–65 cm: sizes 0 and 1 both fit.
- Ruffwear: no overlapping sizes in this range.
- Bailey & Coco: 45–50 cm: sizes XS and S both fit; 45–65 cm: sizes S and M both fit; 55–65 cm: sizes M and L both fit.
How to choose:
- Our size finder picks the size where your dog's measurement sits nearer the middle of the range, so the harness can be adjusted either way.
- Ruffwear says that if your dog is right on the border between two sizes and fully grown, choose the larger size6. For a growing puppy that is truly between sizes, Ruffwear also suggests the larger one4.
- For Julius-K9, check the weight ranges too: if your dog's weight only fits one of the two sizes, go with that one5.
- Deep-chested dogs with a narrow waist can slip a loose harness, so if the larger size would only just fit on its tightest setting, the smaller one is usually safer.
Fit checks when the harness arrives
Two-finger rule
You should be able to slide two fingers flat under every strap, and no more6. Tighter than that can rub; looser can slip.
Strap behind the front legs
The strap around the body should sit a little way behind the front legs, not pressed up into the "armpit", where it will rub as your dog walks.
Nothing on the throat
Every strap at the front should sit on the breastbone or low on the chest, not across the throat.
Free shoulders
Watch your dog walk and trot. Its stride should look the same as without the harness. A small study found harnesses can shorten how far the shoulder reaches forward9, so if the stride looks shorter, adjust the fit or try another style.
Check for rubbing
After the first few walks, look behind the front legs, under the chest and around the neck for redness or broken hairs. If you find any, loosen or reposition the harness. If the skin is sore, stop using it and ask your vet.
Escape test
With the harness on, gently pull the lead forwards, then backwards and upwards. The harness shouldn't slide over the shoulders or ribs. If it does, tighten it, or choose a design with an extra strap behind the ribcage.
Re-check after a week
Webbing and buckles can settle in the first few walks. Check the two-finger fit again after a week.
Harness styles that suit a French Bulldog
Y-front harness that sits low on the breastbone
Keeps every strap well away from the throat, which matters for a flat-faced dog.
Breathable, lightweight materials
Flat-faced dogs can struggle in the heat3, so avoid thick, padded vests on warm days.
Escape-resistant design (extra strap behind the ribcage)
A Frenchie's waist is narrower than its chest, so a second strap further back makes it much harder to reverse out of the harness.
Be careful with
- Any harness with a strap across the front of the neck or throat.
- Head collars. They sit on the face, which is a poor fit for a short muzzle.
- Thick, fully padded vests in warm weather.
Common mistakes
- Walking a Frenchie on a collar and lead instead of a harness. The RSPCA recommends a harness for flat-faced dogs3.
- Choosing a size by weight. Frenchies are heavy in the chest and light behind, so chest girth is the number that counts.
- Letting the harness twist to one side, which usually means it is too loose.
- Measuring the neck instead of the chest. Harness sizes are set by chest girth.
- Assuming a size letter means the same thing in every brand. A Medium in one brand can be a Large in another, so check each chart in centimetres.
- Buying a size up "to grow into" for a puppy.
A note on health
If your French Bulldog breathes noisily, tires quickly or struggles on walks, talk to your vet. A harness helps take pressure off the neck, but it doesn't treat breathing problems.
Collar and ID tag: the UK rule
In the UK, a harness doesn't replace a collar. A dog in a public place must wear a collar with the owner's name and address on it, or on a tag or plate attached to it10. Many owners clip the lead to the harness and use the collar for ID.
French Bulldog harness questions
What size harness does a French Bulldog need?
An adult French Bulldog usually has a chest of 45–65 cm and weighs 8–13 kg1. That usually means Julius-K9 IDC Powerharness: sizes Mini-Mini or Mini; Ruffwear Front Range Harness: sizes XS or S; Bailey & Coco Trail & Glow Harness: sizes S to L. Measure your dog's chest to get the exact size.
How do I measure my French Bulldog for a harness?
Stand your dog square, then wrap a soft tape around the widest part of the chest just behind the front legs4. Keep it flat and snug and read it in centimetres. Measure twice. See our full guide to measuring your dog.
What size harness for a French Bulldog puppy?
Size a puppy on its chest measurement today, not its expected adult size4. Measure every couple of weeks while it grows fast and move up a size when its chest reaches the top of the current size.
What if my French Bulldog is between two harness sizes?
Should a French Bulldog wear a harness or a collar?
Why does my Frenchie's harness twist to one side?
Usually because it is too loose around the chest, or the neck strap is too big. Tighten to the two-finger fit. If it still twists, a design with a wider chest plate may sit better on a barrel chest.
My Frenchie keeps slipping out of its harness. What can I do?
Check the fit first. If it's snug and your dog still backs out, choose a harness with a second strap behind the ribcage. Because a Frenchie's waist is narrower than its chest, that strap is very hard to pull over the ribs.