If you have a flight coming up, you might be wondering if your backpack will count as a carry on, a personal item, or neither, and you will be forced to check it in.

Whether a backpack counts as a carry on, personal item or checked bag depends on both its size and weight according to airline policies.

Generally, personal items have a size restriction of 17 inches long, 10 inches wide and 9 inches high, and must be able to fit underneath the seat in front of you.

Carry on items must generally be no larger than 22 inches long, 14 inches wide and 8 inches high.

Having said that, weight and size restrictions vary by airline, though usually not by too much.

What the Airlines Say

To see whether your backpack counts as a carry on, personal item or checked bag, it’s time to get the tape measure and scale out, and then refer to the following weight and size restrictions for each airline.

Alaska Airlines

  • Carry-on luggage size: 22” x 14” x 9”
  • Carry-on luggage weight limit: Not specified
  • Personal item: Must fit under the seat in front of you
  • Additional Restrictions: One carry-on and one personal item is allowed free of charge

Allegiant Air

  • Carry-on luggage size: 22” x 14” x 9”
  • Carry-on luggage weight limit: Not specified
  • Personal item: 7” x 15” x 16”
  • Additional Restrictions: One personal item is allowed free of charge

American Airlines

  • Carry-on luggage size: 22” x 14” x 10”
  • Carry-on luggage weight limit: Not specified
  • Personal item: 18” x 14” x 8”
  • Additional Restrictions: One carry-on and one personal item is allowed free of charge

Delta

  • Carry-on luggage size: 22” x 14” x 9”
  • Carry-on luggage weight limit: Not specified
  • Personal item: Must fit under the seat in front of you
  • Additional Restrictions: One carry-on and one personal item is allowed free of charge

Frontier Airlines

  • Carry-on luggage size: 24” x 16” x 10”
  • Carry-on luggage weight limit: 35 pounds
  • Personal item: 8” x 18” x 14”
  • Additional Restrictions: One personal item is allowed free of charge

Hawaiian Airlines

  • Carry-on luggage size: 45 linear inches
  • Carry-on luggage weight limit: 25 pounds
  • Personal item: Must fit under the seat in front of you
  • Additional Restrictions: One carry-on and one personal item is allowed free of charge

JetBlue

  • Carry-on luggage size: 22” x 14” x 9”
  • Carry-on luggage weight limit: Not specified
  • Personal item: 17” x 13” x 8”
  • Additional Restrictions: One carry-on and one personal item is allowed free of charge unless you are traveling on a Blue Basic fare ticket

Southwest

  • Carry-on luggage size: 24” x 16” x 10”
  • Carry-on luggage weight limit: Not specified
  • Personal item: 18.5” x 8.5” x 13.5”
  • Additional Restrictions: One carry-on and one personal item is allowed free of charge

Spirit Airlines

  • Carry-on luggage size: 22” x 18” x 10”
  • Carry-on luggage weight limit: Not specified
  • Personal item: 18” x 14” x 8”
  • Additional Restrictions: One personal item is allowed free of charge

United

  • Carry-on luggage size: 22” x 14” x 9”
  • Carry-on luggage weight limit: Not specified
  • Personal item: 17” x 10” x 9”
  • Additional Restrictions: One carry-on and one personal item is allowed free of charge unless you are traveling on a basic economy ticket

When a Backpack Counts as a Checked Bag

If your backpack exceeds an airline’s size and/or weight restrictions for a carry on bag, you will be forced to check it in.

While weight and size restrictions can vary by airline, all major and regional air carriers in the U.S. have an approximate size restriction of 22 inches long, 14 inches wide and 8 inches for a carry on item, and many airlines do not specify a maximum weight limit.

Airlines Don’t Enforce Size and Weight Restrictions That Strictly

Generally, airlines aren’t overly strict if you slightly exceed their size and weight restrictions for carry on and personal items.

It’s actually very unlikely that your carry on or personal item will be weighed, though if it’s suspected that your backpack is clearly over the size limit, a closer look may be taken, and you may be forced to check it in.

Generally, if your backpack looks oversized, you will be asked to place it in the baggage sizer to determine if it is too large to count as a carry on.

And regardless if you’re flying internationally, the same rules apply.

Airlines will enforce the same weight and size restrictions if you are traveling with a backpack on international flights.

You Can Bring a Smaller Backpack With You Too

You can bring two backpacks on a plane as long as one of the bags is able to fit underneath the seat in front of you.

In such cases, one of your backpacks will count as a personal item and the other one will count as a carry on.

Or a Duffle Bag

Whether a duffle bag is considered a personal item or carry on item depends on its size.

Generally, personal items have a size restriction of 17 inches long, 10 inches wide and 9 inches high, and must be able to fit underneath the seat in front of you.

And Definitely a Fanny Pack

Given its small size and the fact that you can wear it around your waist, a fanny pack will count as a personal item.

However, if you are able to fit and place your fanny pack inside your carry on bag, then it won’t even count as a personal item.

Ella Dunham, a Freelance Travel Journalist and Marketing Manager, boasts an impressive career spanning eight years in the travel and tourism sectors.

Honored as one of "30 Under 30" by TTG Media (the world’s very first weekly travel trade newspaper), a "Tour Operator Travel Guru" and "Legend Award" winner, Ella is also a Fellow of the Institute of Travel, a Member of the Association of Women Travel Executives, has completed over 250 travel modules, and hosts travel-focused segments on national radio shows where she provides insights on travel regulations and destinations.

Ella has visited over 40 countries (with 10 more planned this year).