What is Southwest Airlines' carry-on size limit for a 35L bag?

Southwest Airlines' carry-on limit is 24 × 16 × 10 inches (61.0 × 40.6 × 25.4 cm). A 35L backpack fits within that limit on most trips. Southwest's box is notably wider than most US carriers — bags that fit the standard 22 × 14 × 9-inch limit also fit Southwest with additional margin.

Does Southwest have carry-on fees?

No. Southwest Airlines does not charge for carry-on bags. Every passenger is allowed one carry-on and one personal item at no charge, on all bookings. This is a meaningful advantage over airlines that may restrict carry-on access or charge additional fees.

Southwest Airlines Carry-On Rules — What Actually Fits

Will a 35L Backpack Fit on Southwest Airlines?

Q: Will a 35L backpack fit on Southwest Airlines?

Yes. A 35L backpack fits within Southwest Airlines' carry-on limit of 24 × 16 × 10 inches. Southwest's carry-on box is larger than the 22 × 14 × 9-inch standard used by American, Delta, and United. A 35L bag that passes those tighter limits will also pass Southwest's. On a 5-day standard trip in mild weather, packed volume approaches the bag's usable capacity.

Yes. A 35L backpack fits within Southwest's 24 × 16 × 10-inch carry-on limit — and on a 5-day standard trip in mild weather, it approaches usable capacity.

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 Packing-Dependent

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 →

Will This Bag Actually Work for Your Trip?

Your result depends on what you pack, not just the bag size.

Trip Setup

Trip Length

Climate

Packing Profile

Laundry Access

Gear & Footwear

Gear

Laptop Bulky Layer

Extra Packed Shoes

Bag & Airline

Bag Type

Bag Size

What do these sizes mean?

Under 25L — Small personal item / daypack
30–35L — Light travel, short trips
35–45L — Standard carry-on range
45L+ — Large carry-on or checked territory

Airline

Add personal item (up to ~25L)

Use this if you plan to bring a second under-seat item like a daypack, tote, or laptop bag.

Traveler

Clothing Size

Based on real clothing volumes and packing behavior

Packing Reality Check

When Does a 35L Bag Work on Southwest Airlines?

Works Well

1–7 day trips with efficient packing
Light or standard packing style
Warm or mild climate
Laundry available at destination
No heavy tech kit
Compression cubes for 7-day setups

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)
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

A 35L backpack fits within Southwest Airlines' published carry-on dimensions of 24 × 16 × 10 inches. Southwest's carry-on box is wider than most US carriers. At 35L, the limiting factor is usable volume — not the dimension box. On a 5-day standard trip in mild weather, packed volume approaches the bag's usable capacity.

Gear

Example Bags for This Setup

Example bags that match this setup based on real packing capacity and airline limits.

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
Use the calculator above to check your exact trip length and packing load

Other bag sizes on Southwest

Will a 25L backpack fit on Southwest? →

Will a 30L backpack fit on Southwest? →

Will a 40L backpack fit on Southwest? →

Will a 45L backpack fit on Southwest? →

Same size on other airlines

Will a 35L backpack fit on Delta? →

Will a 35L backpack fit on United? →

Will a 35L backpack fit on American? →

Will a 35L backpack fit on Ryanair? →

Will a 35L backpack fit on EasyJet? →

Packing guides

What to pack for a 3-day trip →

What to pack for a 5-day trip →

What to pack for a 7-day trip →

What to pack for a 10-day trip →

Not sure if it'll all fit? Try the packing calculator →

Notes

How Accurate Is This?

This tool reflects real-world packing conditions, not just theoretical bag sizes. Results are based on typical clothing volumes, packing efficiency, and common travel setups.

Published airline limits specify maximum external bag dimensions. A 35L backpack fits within Southwest's carry-on range on most trips. Southwest's 24 × 16 × 10-inch box gives more geometry margin than the 22 × 14 × 9-inch standard — packed volume, not the box limit, is the constraint on longer trips.

This is a planning tool, not a guarantee. Airline staff make the final call — packed shape, bag rigidity, and gate-day enforcement all play a role.