Southwest's carrier footprint is generous — about 18.5" long x 13.5" wide — but the height limit is the tightest among the big domestic carriers: published specs run 8.5" to 9.5" tall depending on where you check, and recent guidance trends toward 8.5". If your carrier is a standard 11-inch-tall box, Southwest is the airline where it gets flagged.
Southwest's in-cabin carrier rules
- Max footprint roughly 18.5" L x 13.5" W; height limit 8.5"–9.5" — confirm the current spec when you book
- Soft- or hard-sided allowed; ventilated; pet fully contained, nothing sticking out
- The carrier counts as your personal item — you keep your full carry-on bag
- In-cabin only: Southwest has no cargo pet option, so if your dog doesn't fit under the seat, your dog doesn't fly Southwest
- Plan on $125 each way; two pets of the same species can share one carrier if they genuinely fit
Why low-profile carriers matter here
An 8.5-inch height clearance eliminates most standard carriers in rigid form. This is exactly where compressible, flexible-height carriers earn their keep — they meet the height at boarding and give your dog usable space the rest of the trip. The wide 13.5" allowance actually favors low-and-wide designs over tall boxes.
What to fly Southwest with
- Mr. Peanut's Gold Series V3.0 — flexible height compresses low while holding structure; the design Southwest's tight clearance was made for
- Rover Ready Expandable Carrier — compresses for boarding, expands at the gate so your dog isn't cramped between flights
Full lineup in the travel collection.
Before you fly Southwest with your dog
- Measure your dog's standing height first — the 8.5" clearance is the constraint; our size guide covers how
- Call Southwest to book your pet — spots per flight are limited and there's no cargo fallback
- Test the compressed carrier under a dining chair at home before travel day
- Line it with a leak-proof pad
Airline rules change — Southwest's published height limit has varied across sources this year. This reflects guidance as of June 2026; confirm current requirements with Southwest before you fly. The airline has the final word.
