IATA crate sizing is arithmetic, not shopping. You take four measurements off the standing dog, put them through one formula, and the answer is the minimum internal size of the box. Breed charts and pet shop labels are guesses. The airline checks the dog against the crate at acceptance, and a crate that fails there is a missed flight.
Introduction: the crate is sized to the animal, not the breed
IATA crate sizing starts with a measuring tape and the dog standing up. Four numbers go in, three internal dimensions come out. Nothing about the breed name, the pet shop size label or the crate the dog sleeps in at home enters the calculation.
Most owners buy the crate first and measure afterwards. It feels sensible, because the box is the thing you can see and a shop assistant will happily point at one and call it a beagle size.
The airline does not accept that reasoning. At acceptance a handler looks at your dog inside your crate and decides whether it can stand, sit erect, turn around and lie naturally. If the answer is no, the dog does not fly. So the order is measure, calculate, then buy — the order My Pet Mover uses on every booking out of the Malaysian export corridor.
Here is a short demonstration of the four measurements before we work through what to do with them.
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What IATA Container Requirement 1 actually says
IATA container requirement 1 is the chapter of the Live Animals Regulations that covers domestic dogs and cats. It sets a performance rule first — stand, sit erect, lie naturally, turn around — and then offers a sizing formula to help you meet it.
The distinction matters. The formula is guidance; the four movements are mandatory. A crate that satisfies the arithmetic but stops the dog turning around is still a rejected crate.
The published Container Requirement 1 sheet (Edition 52, January 2026) also lists state and operator variations — countries and airlines adding conditions on top. Those variations never shrink the minimum.
Two things follow from reading it properly:
- The calculated numbers are internal dimensions. The measurement you take off a shop display is external, and the shell of a rigid plastic crate eats several centimetres on every side.
- The largest animal sets the size. If two compatible dogs share a container, both are measured and the bigger one decides the box.
How to measure dog for crate: the four numbers
To measure dog for crate purposes you need A, B, C and D, all taken with the dog standing normally. Length nose to tail root, ground to elbow, width across the shoulders, and ground to the top of the head or ear tip, whichever sits higher.
IATA defines the four inputs precisely, and the precision is where owners slip. The definitions, as published on IATA’s Traveler’s Pet Corner:
- A — length. Tip of the nose to the base or root of the tail. Not the tip of the tail.
- B — elbow height. Ground to the elbow joint on a front leg.
- C — width. Across the shoulders, or across the widest point of the dog if that is wider.
- D — standing height. Floor to the top of the head, or to the ear tip if the ears stand higher.
Then the arithmetic, which is short:
- Internal length = A + ½B
- Internal width = C × 2
- Internal height = D plus the depth of the bedding
The bedding line is easy to skip and it is not optional — absorbent bedding is required, and it lifts the dog off the floor. For clean numbers, stand the dog against a wall, chalk the head and elbow heights, then measure the wall rather than the moving animal.
IATA crate sizing applied to four real body shapes
Four dogs of similar weight can need very different boxes, because width is driven by shoulders and height by ears. Running the formula on four common body shapes shows how far apart the answers land.
Worked IATA Sizing for Four Dog Body Shapes
| Body shape | A / B / C / D (cm) | Internal length | Internal width | Internal height |
|---|---|---|---|---|
| Small companion (Shih Tzu type) | 45 / 18 / 20 / 30 | 54 cm | 40 cm | 33 cm |
| Medium hound (Beagle type) | 62 / 24 / 26 / 41 | 74 cm | 52 cm | 44 cm |
| Large gundog (Retriever type) | 88 / 34 / 32 / 60 | 105 cm | 64 cm | 63 cm |
| Snub-nosed, +10% (French Bulldog type) | 50 / 20 / 24 / 33 | 66 cm | 53 cm | 40 cm |
Illustrative scenario: representative body measurements run through the IATA CR1 formula (A + ½B, C × 2, D + 3 cm bedding), by My Pet Mover, 2026. Licence.
Look at the last two rows. The snub-nosed dog is barely half the retriever’s length, yet its width sits within 11 cm, because a broad chest and the mandatory uplift both push outward.
Where the measurement usually goes wrong
Five mistakes account for nearly every crate we have to swap. Four make the box too small, which is the version that fails at acceptance. One makes it too big, which only costs money.
Typical Deviation From The Correct Dimension, By Mistake
| Mistake | Deviation | Effect |
|---|---|---|
| Height taken to the shoulder, not the ear tip |
27% too short |
Dog cannot sit erect |
| Dog measured sitting or lying down |
18% too short |
Height and length both under |
| Length taken to the tail tip |
16% too long |
Passes, but costs more to fly |
| Snub-nosed 10% uplift skipped |
10% too small |
Rejected on every dimension |
| Bedding depth left out of the height |
7% too short |
Marginal crates tip into failure |
Illustrative scenario: deviations modelled against the four worked body shapes above, by My Pet Mover, 2026. Bars scaled to the largest. Licence.
The pattern is consistent. Errors that shrink the crate come from measuring the wrong landmark; the one that inflates it comes from measuring generously. Only the first kind gets discovered at the counter.
What makes an airline approved pet crate beyond the numbers
An airline approved pet crate has to pass on construction as well as size. Rigid materials, a solid leak-proof floor, ventilation on all four sides totalling at least 16% of the side area, metal door hardware, spacers, and a Live Animals label.
IATA does not certify or endorse any crate brand, so “IATA approved” printed on a box is a manufacturer’s claim rather than a certification. Judge the crate against the written standard instead:
- Materials. Fibreglass, metal, rigid plastic, welded wire mesh, solid wood or plywood. An all-mesh container is not acceptable.
- Fastenings. On plastic crates the halves must be bolted, not clipped — metal nuts and bolts in every hole.
- Door. It forms the whole of one end, and locking pins must engage the frame by at least 1.6 cm.
- Ventilation. All four sides, with side and back openings over the upper two-thirds.
- Water access. An open bowl fixed inside, fillable from outside. Bottles do not count.
- Wheels. Removed or disabled before tender.
Most retail crates sold in Malaysia arrive close to compliant and need two small jobs — cable ties at the four door corners and a bolted-through top half. We do both routinely on outbound routes from KLIA.
Send us your four measurements.
We will tell you the crate size the airline will accept and what it does to the freight line on your quote. Check pet relocation pricing →
Why crate size decides most of the freight bill
Air freight charges on the higher of actual weight and volumetric weight. For a crated dog the volumetric figure almost always wins, so the box, not the animal, sets the price of the flight.
Volumetric weight is external length × width × height in centimetres divided by 6,000, the divisor Maersk describes as the IATA industry standard. Run the four worked crates through it and the gap is obvious.
Actual Versus Volumetric Weight For Four Crated Dogs
| Body shape | Measure | Value |
|---|---|---|
| Small companion | External crate (cm) | 61 × 46 × 41 |
| Dog + crate actual | 11 kg | |
| Volumetric (÷6,000) | 19.2 kg | |
| Medium hound | External crate (cm) | 81 × 57 × 61 |
| Dog + crate actual | 21 kg | |
| Volumetric (÷6,000) | 46.9 kg | |
| Large gundog | External crate (cm) | 122 × 81 × 89 |
| Dog + crate actual | 50 kg | |
| Volumetric (÷6,000) | 146.6 kg | |
| Snub-nosed, +10% | External crate (cm) | 71 × 59 × 45 |
| Dog + crate actual | 19 kg | |
| Volumetric (÷6,000) | 31.4 kg |
Illustrative scenario: external dimensions estimated from the internal sizes above plus a typical rigid-plastic shell, volumetric weight on the IATA 6,000 divisor, by My Pet Mover, 2026. Licence.
Volumetric weight beats actual weight in all four cases, by close to three times on the largest dog. That is why one size up “for comfort” is an expensive instinct — and why the channel matters too, as we set out in the comparison of cabin, cargo and excess baggage. Route figures sit on our pricing page.
When to measure a dog that is still growing
Measure a puppy as late as the booking allows. Most medium breeds finish gaining height near twelve months, so a crate bought at six months can be two sizes short by departure.
Required Crate Size As A Medium-Breed Puppy Grows
| Age | Standing height D (cm) | Internal length needed | Internal height needed |
|---|---|---|---|
| 4 months | 30 | 54 cm | 33 cm |
| 6 months | 37 | 66 cm | 40 cm |
| 9 months | 42 | 74 cm | 45 cm |
| 12 months | 44 | 78 cm | 47 cm |
| 15 months | 44 | 79 cm | 47 cm |
Illustrative scenario: modelled growth curve for a medium breed, run through the IATA CR1 formula, by My Pet Mover, 2026. Licence.
The curve flattens between twelve and fifteen months. Before that the crate is a moving target, so borrow a training crate early and buy the flight crate late — after the final measurement, four to six weeks out.
The snub-nosed 10% rule, and why it is not generosity
Snub-nosed breeds require a container 10% larger than the formula gives. It is a breathing measure, not a comfort allowance, and it applies to the calculated dimensions rather than to whatever crate you already own.
Pugs, bulldogs, boxers and Pekingese struggle to shed heat through panting, and IATA advises against moving them in hot weather at all. The regulations reinforce this on the ramp by requiring snub-nosed containers to be stowed as far as practical from other loads, so the animal has the largest available volume of air around it.
Apply the uplift to the calculated figures, then choose the crate. Applying it to the crate you already bought is backwards and usually still lands short. Breed restrictions layer on top of the sizing rules, which we cover in the guide to airline restrictions on snub-nosed breeds.
The 10% is not a kindness. It is the extra air a flat-faced dog needs to regulate its own temperature in a hold.
The other places the crate has to fit
The aircraft is only one constraint. Quarantine stations, checkpoints and the vehicle meeting the flight each have their own limits, so a crate that clears the airline can still create a problem on the ground.
Singapore publishes the clearest example. Its Animal and Veterinary Service states that pet containers exceeding 82 cm long by 64 cm high by 58 cm wide externally must be collected personally by the owner or agent at Changi or Tuas, and that all containers must comply with the current IATA Live Animals Regulations. Anything larger left behind goes to a private contractor and costs more to recover.
Three ground constraints worth checking before you buy:
- The receiving vehicle. A retriever crate at 122 cm long will not go into most saloon car boots.
- Collection rules at the border. As above for moves between Malaysia and Singapore, by air or by road as covered in our piece on driving a dog across the Causeway.
- Arrival handling in Malaysia. Inbound animals clear at KLAQS, where crate handling follows the same standard — see how quarantine at KLIA works.
A working sequence from tape measure to tender
Measure, calculate, convert to external, check against destination limits, buy, modify, then acclimatise. Owners who reverse the first and fifth steps are the ones who end up buying twice.
- Measure the standing dog. Take A, B, C and D against a wall, twice, on different days.
- Run the formula. Length A + ½B, width C × 2, height D plus bedding. Add 10% for a snub-nosed breed.
- Convert to external. Add the shell thickness so you can compare shop specifications and destination limits.
- Check the ground rules. Collection limits at the destination, and the vehicle at the other end.
- Buy and modify. Bolt the halves, cable-tie the door corners, fit an open water bowl, remove wheels.
- Acclimatise. Feed the dog in the crate for several weeks before flight day.
The last step matters more than owners expect. A dog that already sleeps in the crate travels as though it is somewhere ordinary.
Conclusion: measure first, buy last
Get the four measurements right and everything downstream follows — the crate passes, the freight quote is predictable, and nobody is renegotiating at the cargo counter on the morning of the flight.
Crate sizing looks like the small technical bit of a pet move. In practice it is the step that most often sends a booking backwards, because it gets decided early, by guesswork, in a shop. Twenty minutes with a tape measure removes that risk entirely.
Frequently Asked Questions
1. Does the crate have to be bigger than the formula says?
No, but it must never be smaller. The formula produces a minimum, and the mandatory test is that the dog can stand, sit erect, lie naturally and turn around. If it can do all four in the calculated size, that size is correct.
2. Is a soft carrier ever acceptable?
Only in the cabin, and not everywhere. IATA relaxes the rigid-construction rule for in-cabin carriers, but some destinations override that. Singapore, for example, requires a rigid IATA-compliant crate even for in-cabin and excess baggage arrivals, because the animal still has to be moved to the quarantine station.
3. Can my two dogs share one crate?
Sometimes. Two adult animals of comparable size up to 14 kg each that are used to living together may share a container, and the width becomes C × 3. Animals over 14 kg must be crated individually, and some countries require it regardless.
4. Does a bigger crate mean a more comfortable flight?
Not usually. An oversized crate lets the dog slide during turbulence and taxiing, and it raises the volumetric weight you are charged on. Correctly sized beats generously sized.
5. Does “IATA approved” on the box mean it will be accepted?
No. IATA does not certify, approve or endorse any pet container brand or model, so the label is a manufacturer’s claim. Acceptance is decided on the day by check-in or cargo staff against the written standard.
Send us four numbers and we will size the crate for you.
Tell us your dog’s A, B, C and D measurements and the destination, and we will confirm the crate the airline will accept, the modifications it needs, and what it means for your quote.
