Depending on what airlines you've flown in the past, you may have noticed some variation in size requirements. On some budget airlines, you might have even been asked to place your bag in the dreaded sizer, and faced with a large, on-the-spot fee if your bag didn't meet the requirements. 

As some airlines increase their checked bag fees, travelers are increasingly seeking ways to maximize their travel budgets. One of those ways can be travel carry-on only (plus free personal item), or level up and travel personal item only on airlines that charge for carry-on bags (this is packing on hard mode depending on the length of your trip). 

So, what differentiates a personal item from a carry on? 

Is it the wheels? The weight? The size? Frustratingly, the answer may still be "it depends." Some countries have weight requirements as well as length x height x width requirements. For the purposes of this post, however, we'll focus on the United States and the length x height x width sizing requirements for common airlines. 

It's important to note, bag measurements include both the handle and wheels. Purchasing a bag labeled "Carry on size" or "personal item" does not actually mean it will meet the requirements for your needs/airline. 

Carry On Dimensions, by Airline 

(Current as of posting, April 12, 2026 - but please verify)

Delta: 22” x 14” x 9”

United: 22" x 14" x 9"

JetBlue: 22" x 14" x 9" 

Spirit: 22" by 18" x 10" (Note: These are typically NOT included in the base fare)

Frontier: 24" x 16" x 10" (Note: Typically not included in the base fare)

Southwest: 24" x 16" x 10"

Personal Item Dimesions, by Airline

Delta: Doesn't specify, but lists examples such as purse, small backpack, laptop bag 

United: 17" x 10" x 9"

JetBlue: 17" x 13" x 8"

Spirit: 18" x 14" x 8"

Frontier: 18" x 14" x 8"

Southwest: Doesn't specify, just "should fit under the seat in front of you"

*Note: If you're flying overseas with a flight operated by a partner airline, you may need to look into their weight/size requirements. 

So...now what? Do I have to buy a different bag for every airline?

Not necessarily. I'd recommend getting one or two "go-to" bags that work on nearly every flight.