The 10-inch listed depth is an important reminder that capacity alone does not determine carry-on compliance. Some airlines publish a 9-inch depth limit, so travelers should compare the packed dimensions with their airline’s current rules rather than relying only on a “carry-on” label.

Best reason to choose it: built-in packing organization.

Think twice if your airline is strict about bag depth.

5. Peak Design Travel Backpack 30L — Best Compact Travel Backpack

Best for: shorter trips, photographers, and travelers who want one backpack for travel and daily use.

Not every one-bag traveler needs 40 liters.

Peak Design’s Travel Backpack 30L compresses to about 27L and expands to approximately 33L, giving it more flexibility than a fixed-volume pack. The company says both configurations meet international carry-on requirements.

A large rear hatch gives access to the main compartment, while padded laptop and tablet sleeves handle electronics. The pack also includes tuck-away shoulder straps, side bottle pockets, and multiple external carry points.

The shell uses recycled 400D nylon canvas with a 900D bottom liner.

The smaller capacity makes this a stronger choice for travelers who already pack lightly and want something that feels less oversized once they reach their destination.

Best reason to choose it: compact versatility.

Think twice if bulky shoes, winter clothing, or longer trips routinely fill your luggage.

6. Thule Aion 40L — Best for Active and Adventure Travel

Best for: gym gear, beach trips, outdoor travel, and travelers carrying dirty or damp clothing.

The most interesting feature of the Thule Aion 40L is not another laptop pocket.

It includes a removable TPU-lined rolltop section designed to separate items that could transfer moisture, odor, or dirt to the rest of your luggage.

That makes the Aion especially practical for trips involving swimming, hiking, sports, or frequent changes of accommodation.

It also carries a laptop up to 17 inches, has a dedicated bottle pocket, internal compression straps, and exterior zipper sliders that can be locked together.

Thule lists the backpack at 40 L, approximately 20.5 x 13 x 9.1 inches and 3.19 pounds. The exterior uses a waxed 600D polyester canvas with water-resistant treatment.

Best reason to choose it: isolation of dirty or damp gear.

Think twice if you want the lightest possible 40L backpack.

7. Pacsafe EXP45 — Best Anti-Theft Travel Backpack

Best for: travelers who prioritize bag security in busy cities, hostels, and public transport.

No backpack makes you immune to theft, but the Pacsafe EXP45 incorporates more physical security features than a typical travel bag.

Pacsafe lists puncture-resistant zippers, cut-resistant materials and straps, an RFID-blocking pocket, a locking system, and an anchor strap among the bag’s security features.

It also functions as a normal travel backpack with a 45L capacity, padded hip belt, sternum strap, compression straps, luggage pass-through, and padded storage for most 16-inch laptops.

Its official dimensions are approximately 21.7 x 13 x 7.5 inches, and it weighs 3.97 pounds.

The tradeoff is weight. Anti-theft hardware and reinforced construction add mass, so travelers facing strict airline weight restrictions should consider that before buying.

Best reason to choose it: integrated security.

Think twice if ultralight packing is more important than anti-theft hardware.

How We Selected These Travel Backpacks

This guide compares backpacks by current manufacturer specifications, external dimensions, capacity, empty weight, laptop protection, opening style, carrying system, materials, and travel-specific features.

A backpack is not ranked higher simply because it has more pockets.

The most useful travel backpack is the one whose design solves a particular travel problem without creating another one. A 45L pack may offer more room but become inconvenient on a strict airline. An elaborate organizer may protect technology but add

unnecessary weight for a traveler carrying only clothes.

Unless a backpack has been personally tested by the author, manufacturer specifications and independently verifiable information should be clearly separated from firsthand experience.

That distinction matters when comparing travel gear.

What Size Travel Backpack Should You Buy?

For many travelers, 35L to 40L provides the best balance between packing space and carry-on practicality.

A 25L to 30L backpack works better for weekend trips and experienced minimalists. A 35L pack gives more flexibility without becoming excessively bulky. Around 40L is a practical target for longer one-bag trips, while 45L pushes closer to the upper end of carry-on travel.

But liters are only an estimate of internal capacity.

Airlines check external dimensions, not the number printed beside the backpack’s model name.

Delta currently publishes a maximum carry-on size of 22 x 14 x 9 inches. American Airlines and JetBlue publish similar standard overhead limits. Other carriers, especially international and low-cost airlines, can use different dimensions or weight limits.

Always check the operating airline before departure.

30L vs 35L vs 40L vs 45L Travel Backpacks