Last Updated on December 1, 2021
This topic is more complicated that it should be.
There isn’t any national agency or organisation that regulates how big a carry-on bag can be. Not directly, not with a size limit in inches.
Each airline sets their own size limits depending on the type of planes they are flying and how they position their brand commercially.
Broadly speaking, when you pay a higher price for your ticket you are more likely to be allowed a big carry-on whereas if your flight ticket is low-cost then the airline might want to charge you to bring a big carry-on bag.
There is a legal limit to how big carry-on luggage can be and it comes from the FAA indirectly from their rules about luggage storage on the plane during take-off and landing.
So I’m going to tell you the rule about how big a carry-in can be but it’s not going to help you much because your airline rules will be smaller.
After that we’ll discuss how big a carry-on you should buy. That’s a better question. It’s smaller than the legal limit and depends on what type of traveler you are.
How Big Can Carry-On Luggage Be According To The Federal Aviation Authority?
In the United States any passenger airline must get a certificate from the Federal Aviation Authority (FAA).
The Federal Aviation Regulations prohibits the airline from closing the plane door unless every carry-on bag has been safely stowed either in the overhead bin or under a passenger seat.
If your carry-on bag is too big to fit in the overhead bin the airline is not legally allowed to close the door and the plane cannot take off.
So the size of the overhead bin legally determines how big your carry-on can be. Most airlines publish size limits that are a little smaller than the overhead bin size, and they enforce those limits by checking how big your carry-on bag is using those metal bag sizers.
It’s left up to each airline to tell their passengers how big a carry-on bag can be in inches. Some airlines also impose a weight limit for carry-on bags.
Some airlines such as Southwest allow a big carry-on suitcase (24 x 16 x 10 inches), but if you buy carry-on luggage that big then it will be too big for almost every other airline in the world.
In the US there is almost a consensus that a carry-on bag can be as big as 22 x 14 x 9 inches.
Alaska, Allegiant, American Airlines, Delta, JetBlue, and United all publish a 22 x 14 x 9 inches carry on luggage size limit.
But that consensus is at risk because more and more airlines are charging for carry-on luggage if you fly at their cheapest prices.
JetBlue and United have basic economy fares that don’t allow you to carry-on a bag as big as 22 x 14 x 9.
Budget airlines like Spirit and Frontier also don’t allow a big carry-on bag by default.
To really understand how big your carry-on can be you need to first understand the two types of hand luggage and then you need to check what the airline you are flying with allows for the ticket class you are flying with.
See what I mean? More complicated than it should be!
The Two Types Of Hand Luggage
The average passenger thinks that a carry-on bag is the bag that you carry on to the plane.
Makes sense right? You carry it on… so it’s the ‘carry-on bag’.
But in the aviation industry they have two types of hand luggage bags. They are both carried on to the plane but only one is called ‘the carry-on bag’.
The two types of hand luggage are the Carry-On Bag and the Personal Item Bag. I’ve talked elsewhere about the difference between the personal item and the carry-on.
There are two types of carry-on bag because of those FAA rules that luggage must be stored before closing the plane door.
Roughly speaking, the carry-on bag goes in the overhead bin and the personal item bag goes under the seat in front of you.
A lot of travelers forget about the personal item bag allowance because they think it’s not very big. Airlines often refer to a personal item as a handbag, purse, laptop bag, or briefcase, but the personal item size limits are usually a lot larger those examples would suggest.
Importantly, a lot of budget airlines and basic economy fares don’t allow you to bring a carry-on bag without paying extra.
But every airline allows you to bring a personal item bag for free.
For example, all Spirit Airlines passengers can bring a personal item bag that is 18 x 14 x 8 inches.
To Joe Bloggs, the carry-on size limit for Spirit airlines is 18 x 14 x 8 inches, but technically that’s their personal item size limit. Their carry-on size limit is 22 x 18 x 10 inches but you’ll need to pay extra for that.
How Big A Carry-On Bag Should You Buy?
That’s a better question to ask.
If you only fly in the US then you should probably buy a carry-on bag no bigger than 22 x 14 x 9 inches. A carry-on bag that big will be usable with most traditional airlines if you don’t buy their basic economy fares.
But if you fly with budget airlines like Spirit or Frontier you won’t be able to use a 22 x 14 x 9 bag without paying extra.
If you travel internationally I recommend buying a carry-on that is no bigger than 21 x 14 x 8 inches. That won’t be suitable with every airline in the world, but it will go a long way to getting you a carry-on bag size that you can use worldwide.
If you take a lot of weekend breaks and like to get the cheapest flight prices then consider buying a personal item bag at 18 x 14 x 8 inches.
22 x 14 x 9 inches luggage has a theoretical maximum capacity of 45 litres, that’s how big your carry-on can be. But remember airlines count the wheels, so if you buy a spinner carry-on with protruding spinner wheels and handles then the space inside your bag will be more like 40 litres.
If you buy a well-designed 18 x 14 x 8 inches bag then it can be as big as 33 litres. That’s 80% as big as a carry-on bag but you’ll be able to take it on almost every airline. If you learn to travel lighter then you might be able to make that work and snag yourself some cheap flights.
Only United has a weird personal item size limit smaller than the other airlines that hardly suits any bags.
When figuring out how big your carry-on can be there is no substitute for checking out the rules for the airlines you want to fly with.
The Verdict
It’s not easy to say how big a carry-on bag can be without knowing which airlines you want to fly with.
A carry-on bag should not be larger than 22 x 14 x 9 inches for most airlines in the United States including wheels and handles.
If you fly basic economy or budget airlines then be aware that you might not be permitted to take a carry-on bag at all.
The bag that you’ll carry on in that scenario will be the personal item bag. That’s often 18 x 14 x 8 inches or similar but check with the airline you are flying with.
If you learn to travel light you can use the personal item bag as your main carry-on and save yourself a lot of money.