Southwest Airlines Carry-On Rules — What Actually Fits
Will a 35L Backpack Fit on Southwest Airlines?
Southwest Airlines’ 24 × 16 × 10 inch carry-on limit accommodates a 35L backpack in most packing scenarios.
Trip length and packing style determine whether everything fits. Shorter lighter trips have room to spare; longer or heavier setups start to push the bag's limits.
Placement: Carry-On (Overhead Bin)
Confidence: Medium–High
Best For: 3–5 Day Trips
Last updated: March 2026
Southwest Airlines allows carry-on bags up to 24 × 16 × 10 inches — wider and taller than the 22 × 14 × 9-inch standard used by American, Delta, and United. A 35L backpack fits that box. Whether your trip fits the bag depends on how many days you're traveling and how you pack.
Check if this will actually fit your trip →
Gear
Bags That Work on Southwest at 35L
Based on Southwest Airlines’s 24 × 16 × 10 in carry-on limit and real bag dimensions.
Safe Pick
Thule Subterra Backpack 34L
34L at 20.5 × 12 × 9 in. Comfortably within Southwest carry-on limits.
Check price →
Rolling alternative
Travelpro Maxlite 5 Compact Spinner
38L rolling carry-on at 22 × 14 × 9 in. A structured alternative when a backpack isn't ideal.
Check price →
We may earn a commission from purchases — disclosure
Stay Carry-On Only
This setup exceeds typical carry-on capacity. Add a personal item or check a bag.
Gear
Recommended Bags for This Trip
These recommendations are based on real bag dimensions compared to Southwest carry-on limits, plus how well each bag fits a 35-liter packing load.
Packing Reality Check
When Does a 35L Bag Work on Southwest Airlines?
Works Well
- 5–7 day one-bag trips — the ideal carry-on size on Southwest
- All 737 flights with standardized overhead bins
- Any boarding position — 35L never draws enforcement attention
- Mixed-climate trips with layers and a laptop
Watch For
- 5+ day standard or heavy packing without laundry
- Cold-weather gear adding bulk
- Large clothing sizes
- No access to laundry on longer trips
Published Carry-On Limits
Southwest Airlines Carry-On Rules
| Max dimensions |
24 × 16 × 10 inches (61.0 × 40.6 × 25.4 cm (24.0 × 16.0 × 10.0 in)) |
| Weight limit |
No official limit on carry-on bags |
| Personal item |
Yes — one personal item allowed (under seat) |
| Carry-on fee |
Included on all bookings; no additional fee |
| Checked bags |
First two checked bags fly free on Southwest |
| Fit at 35L |
A 35L bag fits Southwest's carry-on limit — on a 5-day standard trip it approaches capacity; shorter lighter trips have room to spare |
For a full breakdown of size limits, boarding rules, and exceptions, see our airline carry-on rules guide →
Bottom Line
- A 35L bag fits within Southwest's 24 × 16 × 10-inch carry-on limit
- On a 5-day standard trip in mild weather, the bag approaches capacity — shorter lighter trips fit easily
- Southwest includes carry-on at no charge — no fee penalty for bringing a full-size carry-on
Airline enforcement
How Strict Is Southwest With Carry-On Bags?
Southwest is the most forgiving U.S. airline for carry-on bags and overall luggage. Every fare includes two free checked bags — there are no checked bag fees on any Southwest ticket. This removes the economic incentive to push oversized bags into the cabin. Gate agents rarely measure carry-on bags. Southwest's boarding system (A/B/C groups) assigns positions, not assigned seats, so passengers self-select when to board and overhead space is generally available for A and early B groups. Southwest's 737 fleet has standardized overhead bins — no regional jet complications. Weight limits are not enforced on carry-on bags. The most common carry-on issue on Southwest isn't bag size — it's overhead space on full flights for C-group passengers. Since checked bags are free, Southwest travelers often check larger bags voluntarily, which actually reduces cabin congestion. For carry-on enforcement, Southwest is the least stressful U.S. airline by a wide margin.
Size insight
35L Backpack on Southwest: What Actually Changes?
A 35L backpack is the carry-on sweet spot on Southwest. Well within the 24 × 16 × 10 inch limit, this size never draws attention. Southwest's all-737 fleet means consistent overhead bin size across routes — no regional jet surprises. At 35L, you can handle 5–7 day trips one-bag style. If you need more, check a bag for free. Southwest is the airline where 35L feels effortless. No fare class restrictions, no bin anxiety, no fee pressure.
Notes
How Accurate Is This?
Southwest allows 24×16×10 inches—the largest carry-on dimensions among US domestic carriers. This extra space is a real advantage for 30–40L backpacks. Southwest's enforcement is the most relaxed in the US market; sizers are rarely deployed, and slightly oversized bags often pass without question.
The game-changer at Southwest is free checked bags. If your 30L or 40L bag barely fits as a carry-on, you can check it for free instead. This flexibility makes Southwest the most backpacker-friendly US airline for larger packs, especially on longer trips where checked luggage capacity matters.
Southwest's boarding process (open seating, A/B/C groups) means earlier boarding groups secure better overhead bin space. Fly A or B boarding to minimize the risk that bins are full. Weight limits are never enforced on domestic flights.
This is a planning tool to estimate capacity; actual gate acceptance depends on agent discretion and time of year. Southwest's relaxed culture means a 30–40L bag is rarely controversial, even on fuller flights.
