A weekend backpack like a standard 40L backpack is big enough to carry a backpacking sleeping bag, small tent, and pad, as well as extra clothing and layers. Other things you'll need to carry include a small stove, food and basic cookware, plus a water filter/purifier, first aid kit, and navigation tools.
The truth is that if you're looking for a versatile backpack for travelling Europe, South East Asia or even South America, a 40L backpack will (probably) be the perfect size.
This is why most new backpackers think they need a larger backpack to travel, but with some clever organising and good packing cubes, a 40L backpack could just be the perfect size. You'll be incredibly surprised at just how small of a space you can fit everything you need for 3, 6 or even 12 months.
Multiday (3-5 nights; 50-80 liters)These are the most popular backpacking packs sold at REI and they're an excellent choice for warm-weather trips lasting 3 or more days.
This is why most new backpackers think they need a larger backpack to travel, but with some clever organising and good packing cubes, a 40L backpack could just be the perfect size. You'll be incredibly surprised at just how small of a space you can fit everything you need for 3, 6 or even 12 months.
It is the perfect size for travel, just don't pack it full. A 40L backpack half empty weighs essentially the same as a 20L backpack stuffed full. I did 4 months abroad with a GORUCK GR2 34L a few years ago.
Volume: A 45L backpack is the maximum-sized carry on allowed on most US airlines. For international or budget airlines, choose a bag under 40L. If you want to pack ultralight, anything 35L or under can be carried on virtually any airline. Dimensions: The common 45L volume is usually measured as 22 x 14 x 9 inches.
Our smallest Black Hole® Duffel, with a 40-liter volume that's perfect for small loads and long weekends, is made with 100% recycled body fabric, lining and webbing. This carry-on sized duffel meets most airline and train carry-on requirements.
No, it will be too big (assuming it's full or has a rigid frame, like most packs that size do). The biggest backpacks that will usually fit in an overhead compartment are 40L or so.
MEDIUM BACKPACKS (20 – 35L)This capacity range is considered a medium-size backpack and is probably the most popular bag capacity out there. It's great for taking to school or work, depending on the styling, and can also be a great travel pack for taking on a plane.
A good rule of thumb is that if your carry-on bag fits under the seat in front of you, it's considered a personal item. This includes small backpacks, purses, briefcases, laptop bags, etc. Larger bags, including suitcases, must fit in the overhead bin compartment.