What is Alaska Airlines' carry-on size limit for a 40L bag?

A 40L backpack falls in carry-on territory on Alaska Airlines. The published limit is 22 × 14 × 9 inches for overhead bin bags. Whether a specific 40L backpack stays inside that limit depends on the bag's external measurements when packed.

Can I bring a 40L backpack as a carry-on on Alaska Airlines?

Alaska Airlines allows carry-on bags up to 22 × 14 × 9 inches. A 40L backpack is borderline — soft-sided designs typically clear those dimensions, but overpacked bags or rigid frames may push past the depth limit.

Can I bring a 40L backpack and a personal item on Alaska Airlines?

Yes. Alaska Airlines allows one carry-on and one personal item. A 40L backpack typically counts as a carry-on, while a smaller bag such as a daypack or tote fits under the seat.

Alaska Airlines Carry-On Rules — What Actually Fits (and What Pushes the Limit)

Will a 40L Backpack Fit on Alaska Airlines?

Q: Will a 40L backpack fit on Alaska Airlines?

It depends on the bag and packing. A 40L backpack is borderline for Alaska Airlines' carry-on limit of 22 × 14 × 9 inches — soft-sided travel packs generally clear the dimensions, but overpacked or rigid-frame bags may push past the depth limit.

On Alaska Airlines, a 40L backpack usually works as a carry-on — provided it stays within the 22 × 14 × 9 inch size limit and isn’t overpacked.

What goes inside matters as much as the bag — shoes, jackets, and a full tech kit are where 40L bags start to stretch.

Placement: Carry-On (Overhead Bin) Confidence: Medium–High Best For: 3–7 Day Trips

Last updated: March 2026

Alaska Airlines' carry-on limit is 22 × 14 × 9 inches. A 40L backpack typically fits within those dimensions, provided the bag's external size stays within that range when packed — stated volume alone doesn't tell you whether it fits. Overpacking or rigid bags can exceed the depth limit, but carry-on-specific 40L travel backpacks handle it well.

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 bag sizes mean? (in liters)

Under 25L — Personal item range (fits under the seat)
30–35L — Small carry-on for short trips
35–40L — Standard carry-on range (most common)
40–45L — Borderline carry-on (packing-dependent)
45L+ — Exceeds carry-on limits in most cases

See full guide: carry-on size in liters

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

Gear

Recommended Bags for This Trip

These recommendations are based on real bag dimensions compared to Alaska carry-on limits, plus how well each bag fits a 40-liter packing load.

Packing Reality Check

When Does a 40L Bag Work on Alaska Airlines?

Works Well

4–7 day trips
Light or standard packing
Warm or mild climate
Laundry available
No extra shoes packed
Soft-sided bag design

Becomes a Tight Fit

5+ days without laundry
Cold weather gear
Heavy packing style
Laptop and full tech kit
Extra shoes packed
Larger clothing sizes

Published Carry-On Limits

Alaska Airlines Carry-On Rules

Max dimensions	22 × 14 × 9 inches (55.9 × 35.6 × 22.9 cm)
Weight limit	No official limit on domestic routes
Personal item	Yes — one personal item allowed (under seat)
Carry-on access	Generally allowed; may vary by airline and boarding group
Fit at 40L	A 40L backpack is borderline — most soft-sided designs clear the limit, but overpacked or structured bags may not

At 40L, the depth dimension (9 inches / 22.9 cm) is the constraint. Soft-sided carry-on-designed packs generally stay inside the box, but overpacking or rigid frames can push past the limit.

For a full breakdown of size limits, boarding rules, and exceptions, see our airline carry-on rules guide →

Bottom Line

A 40L bag clears Alaska Airlines' carry-on dimensions in most standard packing setups — the depth limit (9 inches) is the constraint to watch
Overpacked or rigid-frame bags can push past the limit — pack discipline matters at this size
Use the calculator above to check your specific trip setup

Other bag sizes on Alaska Airlines

Will a 30L backpack fit on Alaska Airlines? →

Same size on other airlines

Will a 30L backpack fit on United? →

Will a 30L backpack fit on American? →

Will a 30L backpack fit on Southwest? →

Will a 30L backpack fit on Ryanair? →

Will a 30L 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 →

What to pack for a 14-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.

Airline limits are based on external bag dimensions, not listed volume. A 30L backpack clears most carry-on size boxes easily — whether it doubles as a personal item depends on its packed profile and the aircraft's under-seat clearance.

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.

This analysis is based on real packing volumes, airline dimension limits, and how soft-sided bags behave when packed.