A 55L backpack is generally too large to be considered a standard carry-on for most commercial airlines. Most major carriers (like Delta, United, or British Airways) have a size limit of approximately 45 linear inches (usually 22 x 14 x 9 inches), which typically equates to a volume of 35L to 45L. A fully packed 55L bag is usually too tall to fit in the overhead bin "sizer" at the airport. However, there is a "soft-sided" exception: if you under-pack a 55L bag so that it remains squishy and can be compressed to fit the required dimensions, you might get it past the gate agent. Some specific travel-focused backpacks, like the Osprey Farpoint 55, are designed as a "2-in-1" where a 40L main bag is the carry-on and a 15L detachable daypack is your "personal item." To be safe in 2026, if your bag is over 50L, you should expect to check it unless you are flying on a larger widebody aircraft with very lenient gate staff.
Whether a 55L backpack is considered a carry-on depends on the airline’s specific size and weight restrictions for carry-on luggage. Here’s a general guideline:
Size Restrictions: Most airlines have a carry-on size limit of around 22 x 14 x 9 inches (56 x 36 x 23 cm), including handles and wheels. A 55L backpack may exceed these dimensions, especially if it’s packed full and expands.
Weight Restrictions: Airlines also impose weight limits for carry-ons, typically between 15-22 lbs (7-10 kg). A fully packed 55L backpack could easily exceed this limit.
Airline Policies: Some airlines are stricter than others, and budget airlines often have more restrictive carry-on policies. Always check your airline’s specific rules before traveling.
If your 55L backpack exceeds the airline’s carry-on limits, you may need to check it as luggage or pay an additional fee. To avoid issues, consider using a smaller backpack or packing lightly to keep it within the carry-on dimensions and weight.