1
Step 1 - Measure Body Length
Measure from the tip of the nose to the base of the tail along the spine. Record this as A.
Free Tool · IATA Formula · Airline Compliance Check
Cat Carrier Size Calculator: What Size Carrier Does Your Cat Need?
Stop guessing carrier sizes. Enter your cat's four key measurements to get exact minimum carrier dimensions using the IATA-style formula, plus instant airline checks for Delta, United, Southwest, and more.
IATA formula: Length = A + 1/2B, Width = C x 2Most U.S. cabin limits cluster around 18 x 11 x 11 inAdds comfort clearance and flat-faced breed space
Calculate Your Cat's Carrier Size
Recommended Carrier Size
Luna's Recommended Carrier Size
Length
49 cm
19.3 in
Width
31 cm
12.2 in
Height
36 cm
14.2 in
Luna needs at least 49 x 31 x 36 cm (19.3 x 12.2 x 14.2 in), which falls in the M carrier category.
How We Calculated This
Length = 49 cm
42cm(A) + 1/2 x 8cm(B) + 3cm comfort
Width = 31 cm
14cm(C) x 2 + 3cm comfort
Height = 36 cm
31cm(D) + 2cm bedding + 3cm comfort
Delta Air Lines Compliance Check
Your carrier: 49 x 31 x 36 cm
Delta Air Lines limit: 45.7 x 27.9 x 27.9 cm
Status: Non-Compliant
Estimated cat + carrier weight: 6.2 kg / limit 9.1 kg (Weight OK)
- Length: 49cm > 45.7cm limit
- Width: 31cm > 27.9cm limit
- Height: 36cm > 27.9cm limit
Your cat needs a carrier larger than Delta Air Lines's published cabin limit (Length: 49cm > 45.7cm limit; Width: 31cm > 27.9cm limit; Height: 36cm > 27.9cm limit). Consider cargo travel, car travel, or another airline.
View official policyLast verified: 2026-06
Fit Check Tips
- Stand without head or ears pressing into the top
- Turn around in a full circle inside the carrier
- Lie down with legs extended naturally
- Sit upright without hunching
- Stay on a non-slip mat that does not steal too much height
Soft-sided airline carrier
Delta Air Lines expects a flexible carrier that can fit under the seat.
Measurement Guide
How to Measure Your Cat for a Carrier
Take measurements when your cat is calm and standing. A soft tape is easiest, but a string and ruler works too.
2
Step 2 - Measure Elbow Height
Measure from the floor to the elbow joint while your cat stands naturally. Record this as B.
3
Step 3 - Measure Shoulder Width
Measure the widest point across the shoulders. Record this as C.
4
Step 4 - Measure Standing Height
Measure from the floor to the top of the head or ears, whichever is higher. Record this as D.
5
Step 5 - Weigh Your Cat
Use a pet scale or weigh yourself holding your cat, then subtract your own weight.
Quick Reference
Cat Carrier Size Chart by Cat Weight
Weight can estimate a starting point, but body length and height are more reliable. Use the calculator when you can measure your cat.
| Cat Size | Typical Length | Typical Height | Carrier Size | Airline Friendly |
|---|---|---|---|---|
| Kitten / Very Small Cat (< 5.5 lbs) | 25-32 cm | 20-25 cm | XS: 35 x 22 x 26 cm | Usually |
| Small Adult Cat (5.5-10 lbs) | 32-40 cm | 25-30 cm | S: 42 x 28 x 30 cm | Usually |
| Medium Cat (10-13 lbs) | 40-48 cm | 28-33 cm | M: 48 x 32 x 34 cm | Usually |
| Large Cat (13-18 lbs) | 46-55 cm | 30-36 cm | L: 54 x 36 x 38 cm | Often no |
| Very Large Cat / Maine Coon (18-26 lbs) | 55-65 cm | 33-40 cm | XL: 63 x 40 x 42 cm | Often no |
Airline Rules
Airline Cat Carrier Size Requirements (2026)
Always verify with your airline before purchase. Policies change, aircraft vary, and "IATA approved" product labels are not official in-cabin certification.
| Airline | Max L x W x H (in) | Max L x W x H (cm) | Max Weight | In-Cabin |
|---|---|---|---|---|
| American Airlines | 18 x 11 x 11 in | 45.7 x 27.9 x 27.9 cm | 20.1 lbs / 9.1 kg | Yes |
| Delta Air Lines | 18 x 11 x 11 in | 45.7 x 27.9 x 27.9 cm | 20.1 lbs / 9.1 kg | Yes |
| United Airlines | 18 x 11 x 11 in | 45.7 x 27.9 x 27.9 cm | 22 lbs / 10 kg | Yes |
| Southwest Airlines | 18.5 x 13.5 x 9.5 in | 47 x 34.3 x 24.1 cm | 24.9 lbs / 11.3 kg | Yes |
| Alaska Airlines | 17 x 11 x 9.5 in | 43.2 x 27.9 x 24.1 cm | 20.1 lbs / 9.1 kg | Yes |
| JetBlue | 17 x 11 x 11 in | 43.2 x 27.9 x 27.9 cm | 20.1 lbs / 9.1 kg | Yes |
| British Airways | 24 x 18 x 18 in | 61 x 45.7 x 45.7 cm | 70.5 lbs / 32 kg | No |
| Lufthansa | 21.7 x 15.7 x 9.1 in | 55 x 40 x 23 cm | 17.6 lbs / 8 kg | Yes |
| Air France | 18.1 x 11 x 9.4 in | 46 x 28 x 24 cm | 17.6 lbs / 8 kg | Yes |
| Emirates | 24 x 18 x 18 in | 61 x 45.7 x 45.7 cm | 70.5 lbs / 32 kg | No |
Airline policies change frequently. This table was last verified June 2026. Always check the airline's official website before purchasing a carrier or booking travel.
Carrier Guide
What Size Cat Carrier Do You Need?
Understanding the IATA Carrier Size Formula
The formula starts with four body measurements: length A, elbow height B, shoulder width C, and standing height D. Minimum length is A + half of B, width is C x 2, and height is D plus bedding.
Soft-Sided vs Hard-Sided Carriers
Soft-sided carriers are usually best for in-cabin airline travel because they can flex slightly under the seat. Hard-sided carriers are better for cargo, car restraint, and cats that need more structure.
Special Cases: Large Cats, Kittens & Flat-Faced Breeds
Large cats may need a carrier that exceeds cabin limits. Kittens still need secure footing, not an oversized box. Flat-faced breeds need extra ventilation space and should avoid cargo whenever possible.
Signs Your Cat Carrier Is Too Small
A carrier is too small if your cat cannot stand, turn around, lie down naturally, or sit without hunching. Refusing to enter, panting, or staying pinned in one position can also signal a poor fit.
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Carrier fit
A good carrier fit balances measurement, comfort, ventilation, and travel rules
Carrier sizing is not just length by width by height. The best result gives your cat room to stand, turn, and lie naturally while still fitting the travel use case, airline limits, ventilation needs, bedding, and weight restrictions.
Result guide
How to interpret the recommended dimensions
The minimum size is a fit calculation. The recommended size adds comfort clearance and special adjustments when needed. For airline travel, the final decision also depends on external carrier dimensions, soft-sided flexibility, combined weight, and the airline's current pet policy.
- Measure nose-to-tail base, elbow height, shoulder width, standing height, and weight.
- Use internal dimensions for cat comfort and external dimensions for airline compliance.
- Flat-faced breeds need extra airflow and should not be packed into the smallest possible space.
- A cat should be able to stand, turn around, sit naturally, and lie down without being compressed.
Internal and external size differ
Thick walls, wheels, padding, and frames can make the usable interior smaller than the product listing suggests.
Airline fit is policy-specific
A carrier that fits one airline may fail another, and policies can change, so the calculator's comparison should be confirmed before booking.
Comfort affects stress
A carrier that is technically allowed but cramped, poorly ventilated, or unstable can increase fear, heat stress, and refusal.
Travel decisions
Choose the carrier around the trip, not only the cat
The same cat may need a different best carrier for a vet visit, car ride, in-cabin flight, cargo route, or emergency evacuation. Use the size result as the fit baseline, then apply the travel context.
Vet visits
Ease of loading, top access, cleanability, and stable footing often matter more than the smallest possible footprint.
Choose a carrier that opens widely and lets the clinic examine the cat with less forced handling.
Cabin airline travel
Airline limits usually apply to external dimensions, while comfort depends on internal space. Soft-sided flexibility can help, but only within policy.
Confirm the exact airline policy before purchase and again before travel.
Large or flat-faced cat
Large cats need real turn-around room, and flat-faced breeds need extra ventilation. A barely compliant carrier may not be humane for long travel.
Prioritize internal height, airflow, and comfort clearance over minimal size.
Before buying
Compare product internal dimensions, external dimensions, and return policy.
Before flying
Reconfirm airline dimensions, weight rules, reservation process, and documents.
After growth or weight change
Re-measure kittens, large breeds, or cats whose body condition changes.
How to choose after calculating
1
Compare listed dimensions carefully
Check whether a product reports internal or external dimensions and leave room for bedding.
2
Test the turn-around rule
Let the cat enter at home and confirm they can turn and settle without the lid forcing posture.
3
Verify the travel policy
Before flying, confirm the airline's current size, weight, reservation, and documentation requirements.
FAQ
Frequently Asked Questions About Cat Carrier Sizes
What size cat carrier do I need?
Use the IATA-style formula: carrier length equals nose-to-tail length plus half of elbow height, carrier width equals shoulder width times two, and carrier height equals standing height plus bedding thickness. Add comfort clearance so your cat can stand, turn around, and lie down.
How do I measure my cat for a carrier?
Measure body length from nose to tail base, elbow height from floor to elbow, shoulder width at the widest point, standing height from floor to head or ears, and current weight. A soft measuring tape is easiest.
What are the airline requirements for cat carriers?
Many major U.S. airlines publish in-cabin carrier limits around 18 x 11 x 11 inches, while Southwest and several international airlines differ. Combined cat plus carrier weight is often capped around 20-25 lb or 8-11 kg. Always check the airline before booking.
Is my cat carrier too small?
A carrier is too small if your cat cannot stand without touching the top, turn around, sit naturally, or lie down with legs extended. A poor fit can also cause refusal, panting, and stress during travel.
What size carrier for a large cat?
Large cats often need carriers around 20-24 inches long with enough width and height to turn around. Many large cats exceed in-cabin airline limits, so car travel or cargo options may be necessary.
Do flat-faced cats need a bigger carrier?
Yes. Flat-faced cats such as Persians, Exotic Shorthairs, and some British Shorthairs need extra ventilation space. This calculator adds 10% to the recommended size for flat-faced breeds.