The Best Travel Backpack for Europe Is 35–40L and Boring

35–45L, and the Ryanair problem

Forty-five litres is the ceiling that still fits most European overhead bins when packed as a rectangle. Fifty litres is a checked bag pretending to be a backpack. Thirty litres works if you already own a travel capsule and wash merino in the sink. Most people land at 35–45L because of shoes, not shirts.

Airlines do not care about liters. They care about centimeters and, on the cheap carriers, kilograms. Ryanair’s free “small bag” is 40×25×20 cm and goes under the seat. Cabin with priority is 55×40×20 cm. EasyJet and Wizz have their own numbers and they move. A branded “40L carry-on” will often slide into a 55×40×20 sizer and fail 40×25×20. If you refuse to pay for priority, you are shopping for a 20L under-seater plus a small crossbody, not a travel backpack.

Clamshell, hip belt, weight

A clamshell zip lets the bag lie open like a suitcase so packing cubes land in a grid. A top-loader is a hiking bag; you will unpack the whole thing to find socks. Look for a padded sleeve that actually fits a 14–16 inch laptop if you work, the same test you would run on a work bag, and a front dump pocket that is not the only security.

Hip belt: you want one if any day of the trip is 20 minutes of walking with the bag on, which in Europe is most days. You want it stowable so it does not catch the overhead bin. Shoulder straps that can be tucked behind a zippered panel turn the pack into a luggage-like slab for the sizer.

Empty weight is the spec brands hide. 1.2–1.6 kg empty is the useful band. Over 2 kg empty means you have already spent a third of a 10 kg Ryanair limit on nylon. Osprey Farpoint/Fairview 40, Cotopaxi Allpa 35, Aer Travel Pack 3, Peak Design Travel Backpack (45L is tight on some sizers), and the smaller Patagonia Black Hole MLC sit in the $180–320 band and the right weight. A $55 generic 40L on a marketplace is often 2.2 kg of spongy foam.

Anti-theft is mostly marketing

Slash-proof mesh, hidden lockable zippers, and RFID pockets are sold to people watching pickpocket videos. In Paris, Barcelona, and Rome the actual failure is an open zip on a hip pack in a metro crowd, not a knife through ballistic nylon in a museum queue. A zipper panel that sits against your back is useful. A 400 g “security” subframe is a hike you did not book.

Lock the bag in a hostel if you need to. Use a small cable lock through the zipper pulls in a sleeping-car. Do not buy a backpack because the listing says anti-theft seven times. Buy it because it is 35–45L, clamshell, 1.2–1.6 kg, and has a hip belt you can hide.

What to put in it

Two pairs of shoes including the ones you wear on the plane, a merino-heavy capsule, packing cubes, a 1L toiletry that will actually go through security, and a layer for the cabin. That is a 35L pack. The third pair of shoes is how you meet the sizer. Wear the bulky thing on the flight — the logic in what to wear on a long flight — instead of packing it.

Skip the full-size towel, the “just in case” blazer in a bag, and a camera cube that turns 40L into 40L of foam. If you need a second bag, a packable tote for the market day is lighter than a 50L “just in case” backpack you will hate on cobbles.