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What Size Dog Door Do I Need? An Australian Sizing Guide
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What Size Dog Door Do I Need? An Australian Sizing Guide
Work out what size dog door you need from three measurements: your dog's shoulder height, their widest point, and their chest height off the ground. The first two point you at a model. The third — the one almost everyone skips — sets the height you install it at, and getting that wrong is a more common reason a dog refuses a new door than getting the size wrong.
Five minutes with a tape measure now saves a return, or a second hole in your glass. Here's the whole process.
Three measurements, five minutes
1Shoulder height
Stand your dog square on a flat floor. Measure from the ground to the top of the shoulder blades — the withers, not the top of the head. Dogs duck slightly as they step through a doorway; they don't need clearance for their skull.
2Widest point
Measure across the widest part of the body. In deep-chested breeds — Staffies, Boxers, Greyhounds — that's the chest. In others, such as Corgis or a Labrador carrying a bit of extra weight, it's the hips. Measure both and use the larger figure.
3Chest height from the ground
Measure from the floor to the bottom of the chest, at the point furthest from the ground. This number does not choose your model — it sets your installation height, which is the next section.
Two dogs: size for the larger one. The smaller dog will manage a bigger flap without complaint. The reverse is not true.
Between two sizes: go up. A dog that has to squeeze stops using the door.
Matching your measurements to a model
Every Catwalk® and Dogwalk® model is published with the animal it suits, so you don't need to calculate anything. Find the row that covers your dog, then check the fitting column against the door or glass you're putting it into.
| Model | Flap (W × H) | Fits into | Suits |
|---|---|---|---|
| W-CDW / W-CDB slim line cat door | 155 × 170 mm | Timber, composite, metal, uPVC — 11–30 mm | Cats, very small dogs |
| W-CDTW / W-CDTB tunnel cat door | 155 × 170 mm | Panels and walls 11–52 mm | Cats, thicker walls |
| G-CDW / G-CDC glass cat door | 165 × 193 mm | Glass 3–10 mm | Cats |
| G-SDDC / G-SDDW / G-SDDB maxi | 187 × 203 mm | Glass 3–28 mm | Large cats, small dogs |
| W-SDDW / W-SDDB small dog door | 180 × 240 mm | Panels 11–30 mm | Small dogs |
| W-SDDTW / W-SDDTB small dog tunnel | 180 × 240 mm | Panels and walls 11–52 mm | Small dogs, thicker walls |
| G-IDD intermediate dog door | 216 × 250 mm | Glass 4–32 mm (slimline 4–13 mm) | Small to medium dogs |
| G-DDW / G-DDC / G-DDB glass dog door | 270 × 313 mm | Glass 3–32 mm | Medium to large dogs |
| W-DDW / W-DDB timber dog door | 270 × 320 mm | Panels 5–36 mm | Medium to large dogs — the tallest flap in the range |
Two things worth noticing in that table. The widest flap we make is 270 mm, and the glass G-DDW and the timber W-DDW share that width — the timber model is simply the taller of the two, 320 mm against 313 mm. Width alone will not decide between glass and timber; the panel you are fitting into will. And the glass models each have a thickness range; that range, not your dog, is what rules a model in or out once you've chosen where it's going.
Width: the flap should be at least your dog's widest point plus 25 mm.
Height: the flap should be at least your dog's body depth plus 25 mm. Body depth is measurement 1 minus measurement 3 — shoulder height less chest height off the ground — because the flap is fitted with its base at chest level, so it only has to clear the body, not the whole dog.
The Suits column above already satisfies both for a typical dog of that size. Use these two checks when your dog sits near the top of a range, or is unusually broad for its height.
If you'd rather not read a table, the Find Your Fit tool asks four questions and returns the model plus the exact cut-out diameter to hand to a glazier.
Timber dog doorsGlass dog doors
A rough guide by breed
A starting point for narrowing the field — not a substitute for measuring the dog in front of you. Individuals vary a long way inside a breed. For a longer list — around thirty breeds with the flap size for each — see our dog door size by breed guide.
| Breed | Typical shoulder height | Start by looking at |
|---|---|---|
| Chihuahua, Toy Poodle, Maltese | 180–230 mm | Cat door, or the W-SDD small dog door |
| Cavoodle, Jack Russell, Mini Dachshund | 250–330 mm | W-SDD, or G-SDD maxi in glass |
| Corgi, Beagle, Mini Schnauzer | 300–380 mm | W-SDD or G-IDD intermediate |
| Staffordshire Bull Terrier, Cocker Spaniel | 360–430 mm | G-DDW or W-DDW |
| Border Collie, Kelpie, Blue Heeler | 430–510 mm | G-DDW or W-DDW — measure the widest point carefully at the top of that range |
| Labrador, Golden Retriever | 530–610 mm | G-DDW or W-DDW — most fit comfortably, but measure the widest point first |
Width is what decides it at the top of the range, not height — a broad-chested dog can be a tighter fit than a taller, leaner one of the same weight. If yours is close to the limit, send us the three measurements and we'll tell you honestly whether it will work.
Can't see your breed above? The breed-by-breed guide covers thirty of the most common dogs in Australian homes, band by band.
Installation height — the part that decides whether it gets used
A correctly sized flap fitted at the wrong height gets ignored. The rule is simple: the bottom of the flap opening should sit level with, or slightly below, the bottom of your dog's chest. That's the third measurement you took.
Fitted that way, your dog steps through at its natural walking height rather than climbing or crouching — which is also why the flap itself doesn't need to be as tall as the whole dog.
| If it's fitted too high | If it's fitted too low |
|---|---|
| Your dog has to step or jump up into it | Your dog has to duck and crouch |
| Hard on hips and joints in older dogs | The flap catches on their back |
| Puppies and small dogs can't reach it at all | Rain runoff and leaf litter get pushed inside |
| The most common reason a dog "won't use" a new door | Weakens the panel below the opening |
For cats, aim for the bottom of the flap 100–150 mm above floor level. For dogs, work from the chest measurement. If it is a cat you are sizing for rather than a dog, our cat door sizing guide covers the cat models and the measurements that matter for them.
Where it's going narrows the field again
Your dog's size shortens the list. The door or window you're fitting into shortens it further — and in glass, thickness is decisive.
| You have | What to check | What fits |
|---|---|---|
| Timber, composite or uPVC door | Panel thickness | W-CD / W-SDD models 11–30 mm; W-DD 5–36 mm |
| A thicker door, or going through a wall | Total thickness | Tunnel models, 11–52 mm |
| Single-glazed window or slider | Glass thickness | G-CD 3–10 mm; G-DD 3–32 mm |
| Double glazing | Unit thickness | G-SDD maxi to 28 mm; G-IDD to 32 mm |
| A security screen as well | Both need solving | Plan the screen and the door together |
Fitting into glass changes the cost picture considerably, because in most Australian homes the panel has to be replaced rather than drilled — we break that down in what it costs to install a pet door in glass, and cover the double-glazing and toughened-glass cases in this guide. For a slider specifically, dog doors for sliding glass doors covers the three routes.
Any qualified glazier or carpenter can fit these — there's nothing proprietary about the installation. Our installer directory lists independent fitters across Victoria, NSW, Queensland and WA.
Common questions
What size dog door do I need?
Measure your dog's shoulder height, their widest point, and their chest height off the ground. The first two point you at a model in the size chart above; the third sets the height you install it at. If your dog falls between two sizes, go up.
How do I measure my dog for a dog door?
Three measurements with the dog standing square on a flat floor: shoulder height at the withers, the widest point across the chest or hips, and the height from the floor to the bottom of the chest.
Is it better to size a dog door up or down?
Up. A dog that has to squeeze through will stop using the door altogether. An unnecessarily large flap moves a little more air and needs a bigger cut-out in glass, but it still gets used.
What size dog door should I get for a puppy?
Size for the adult dog, using the breed's typical adult shoulder height rather than the puppy's current size. Replacing a door and a glass panel a year later costs far more than the larger unit.
Can two dogs of different sizes share one dog door?
Yes. Size the flap and set the installation height for the larger dog — smaller dogs manage a bigger flap easily.
How high off the ground should a dog door be installed?
The bottom of the flap should sit level with, or just below, the bottom of your dog's chest, so they step through at walking height. Too high strains older dogs; too low lets water and debris inside. For cats, 100–150 mm above floor level.