What is the Best Size for a Travel Backpack?

This article is your quick guide to understanding travel backpack sizes.

Most backpacks are between 25 and 85 liters. That range is huge. What is the best for your trip though?

Smaller bags, starting around 25L, are ideal for use as daypacks. They work well when you're only carrying a few items that you need to keep handy, like a light jacket, book, or camera. Twenty-five liter bags can also be used for short weekend trips if you're a light packer.

Very large bags, 65L and up, are for long hiking trips. These bags work well in the outdoors when you will be carrying multiple days worth of clothing and camping gear.

Bags larger than 65L are too big for travel, even on extended trips. If you'll be traveling for more than a week or two, you'll need to do laundry. Pack light, preferably in a carry on bag, and do laundry every few weeks. Don't carry your entire closet on your back.

Between these two extremes is the sweet spot for luggage size. Thirty-five to forty-five liter packs are ideal for travel. We recommend 45L if you like to pack a little more, and 35L if you prefer to pack light.

The Best Size for a Backpack is Carry On Size

If you have to check your bag, you’re facing luggage fees, waiting at baggage claim, and lost or damaged luggage. The ideal volume for a backpack is a function of its dimensions. Most airlines allow carry-on luggage up to 22" x 14" x 9". You may also see a limit of 45 linear inches (length + width + height). The ideal bag is carry-on-sized and takes full advantage of the airlines' size restrictions.

Unless you're a paragon of light packing, you'll want all the space you can get without having to check your bag.

A bag measuring 22" x 14" x 9" is 2,772 cubic inches in volume. Just multiply the three measurements together. 2,772 cubic inches translates to 45.2 liters.

A 45L bag is the most efficient use of your carry-on luggage allowance. It affords you the most packing space without having to check a bag.

Bags larger than 45L cannot be carried on. If you see a 50L backpack marketed as a carry on, double check the dimensions. It's probably too big to technically qualify as a carry on.

Take every inch the airlines will give you. The ideal backpack is carry-on-sized for:

  • Easy transport: Smaller is lighter
  • Avoiding baggage fees: Save $50 per roundtrip flight
  • Downsizing your luggage: Packing light can be hard, so self-imposed constraints can be a good thing
  • Preventing airlines from mishandling or losing your bag: Keep it on the plane and in your hands, not theirs

On budget airlines, make sure to weigh your bag, even if it is carry-on-sized. Most airlines allow bags up to 22 lbs (10 kg), but budget airlines are more strict and may charge you for the extra weight or force you to check your bag and pay the baggage fees.

If you’re traveling on an airline with stricter dimensions, we recommend choosing a 35L backpack.

It might seem daunting at first, but packing for a long trip in a carry on backpack is totally doable with a little preparation.

While researching bags for a backpacking trip in 2009, we were surprised to discover that most backpacks were too large to be carried onto a plane. Large backpacks were mostly made by outdoors companies without regard for carry-on rules. No one had designed a bag for travelers.

The perfect travel backpack didn't exist; so we made it.

All Tortuga travel backpacks qualify as carry ons. Even when fully packed, the max dimensions for our 45L bags are 22" x 14" x 9" -- exactly the size that airlines allow.

For Organization Enthusiasts

The Outbreaker Backpack combines the ergonomics and portability of a backpack with the obsessive organization and easy packing of a suitcase. With the Outbreaker, you have a place and a compartment for everything.

It’s height-adjustable so you can get the perfect fir and it’s made with waterproof sailcloth so you know your stuff will be safe in a downpour. It even has a TSA-friendly lay-flat laptop compartment.

The Outbreaker Backpack is our most ergonomic, most organized, and most adjustable backpack. The 45L will max out carry on dimensions on most airlines so you never have to check a bag. For stricter airlines, like RyanAir, 35L will be a better choice.

For Light Packers and Short Trips

The Setout Divide Backpack was designed with the light packer in mind. For light packers and short trips, a large carry on is too much bag. Work bags are the right size, but aren’t built for travel. The Setout Divide is just the right size for a weekend or week-long trip.

Expand the backpack from 26L to 34L for extra packing space when you need it. Use the two-compartment layout to separate and organize your clothing.

The Best of Both Worlds

If you like internal organization, lots of packing space, and a hip belt but still prefer a lightweight bag, the Setout Backpack is your holy grail. It has most of the organization and all of the packing space of the Outbreaker in a lighter weight package. It has the right amount of features for most travelers at a more affordable price range.

Compare travel backpacks here to find your perfect backpack for city travel.


Video Transcript

A travel backpack should be small enough to use as a carry on but large enough for up to one week’s worth of clothing. You’ll need space and organization for important toiletries and electronics. Make sure it’s not too heavy; you’ll want to be comfortable as you navigate around your destination. This post offers other tips for choosing a bag that’s the best size for you.