How to size a carrier
Every listing here warns about the same mistake, and it is worth repeating because it is nearly universal: size by dimensions, not weight. Amazon Basics, Henkelion and Sherpa all say some version of “measure your pet’s length and height, do not choose on weight alone.” A long, light dog and a short, heavy dog of the same weight need different bags.
- Length: from the base of the neck to the base of the tail.
- Height: from the floor to the top of the shoulder, with the dog standing.
- The rule of thumb: the dog should be able to stand up, turn around and lie down naturally inside. That is also the substance of what airlines expect for cargo travel.
- If you are between sizes, go up — but not so far up that the carrier no longer fits under a seat, which is the constraint that actually gets you turned away.
In-cabin vs cargo: choose before you shop
If your dog is small enough for the cabin, that is almost always the right answer — it stays with you, in a temperature-controlled space, and you can see it. The features worth paying for are a compressible frame (so it can be pushed down to fit a tighter under-seat space), locking zippers, a waterproof base, and top as well as front entry, because loading a nervous dog from above is far easier than pushing it in from the front.
If your dog is too big for the cabin, you are in hard-kennel territory and the requirements change completely: ventilation on all sides, tie-down points, a secure door with interlocks, and the paperwork — LIVE ANIMAL stickers, ID labels, a food and water cup. Buying a kennel that ships with those items saves an unpleasant scramble the night before. Talk to your vet before booking cargo travel at all, particularly for a brachycephalic (flat-faced) breed, where the risks are well documented.
The carrier as a car restraint
A carrier can double as a vehicle restraint, and two of our picks include the feature that makes that possible: a luggage strap or loop handles that a seat belt can pass through. That matters, because a carrier sitting loose on a seat is a projectile in a crash exactly like an unrestrained dog. If you use one in the car, thread the belt through and cinch it. The AVMA’s safe-transport guidance is built around the same principle — the animal, and whatever contains it, must be secured.