The Ideal Size of a Carry-On Backpack

Updated November 8, 2021

carryon backpack

A backpack is one of the most important travel gears that you can have, and hence you should make absolutely sure that you always carry-on your backpack while traveling in flights. But all airlines have put in place some restrictions on the size of luggage that you can carry-on. So what size should you go for while looking for a backpack that you can carry along with you in flights?

In general, any luggage with physical dimensions of up to 22’’ x 14’’ x 9’’, and weight up to 15 lbs (7 kg) is allowed by most airlines as a carry-on. Note that the dimensions include the wheels of the luggage, the handles, as well as side pockets if any. The dimensions and weight may vary a little with different airlines. There is no official carry-on size for domestic or international travel that all airlines follow. Each has its own set of rules and guidelines.

Though the height, width, and depth measurement may be different for different airlines, almost in all cases the linear measurement (total of the height, width, and depth) comes around 45 inches. This may give you some idea while shopping for a carry-on backpack.

Best Size for a Carry-on Backpack

Backpacks, in general, are measured in terms of volume in liters, based on how much they can hold. You will find backpacks of all sizes and capacities in the market, starting from 15 liters to all the way up to 8o liters.

carry-on backpack

So how do you find one ideal for a carry-on? 

The rule of thumb is to look for something around 35 to 45 liters. That capacity will somewhat ensure a physical dimension within the carry-on limit. However, if you are planning to carry-on your backpack with you in all airlines, you have to be absolutely sure that your backpack meets the most stringent restrictions. In that case, something within 40 liters will be a good choice. 

Apart from the restrictions imposed by the airlines, you should also consider how much weight you are comfortable with on your back. You should be able to move quickly and comfortably carrying that much weight. Unlike wheeled luggage, a backpack will almost always be on your back. In big airports or train stations, you be will walking long distances as well as going up and down escalators and stairs carrying your backpack. Too much load will quickly make you feel miserable. 

Once I had to walk 20 minutes with a backpack to get to a cab from the train station. It was a 45-litre backpack, fully packed, around 14 kgs in weight. On top of it, it had no waist-belt to transfer the weight to the hips. It felt like my shoulders would break from the load it was carrying. That one experience taught me an important lesson. I have never carried that backpack on a journey again. My current backpack is of 35-litre capacity.

Of course, if you are a big strong person, the weight of a fully packed large backpack may not bother you. However, if you already have back problems, you should be very careful regarding the size of the backpack. Also, a thick padded waist belt is a must if you anticipate carrying your backpack for long durations.

Some minimalist travellers carry only one luggage along with them even for long vacations. If you are such a person, you may need a backpack that fits all your belongings.

carry-on backpack

However, you can get by with a small backpack too if you plan to do laundry regularly.

So while deciding on the size of a carry-on backpack, do keep in mind your physical capability, your traveling style, as well as the restrictions imposed by the airlines on the size and weight.

While packing your backpack, always weigh it to be sure you are within the limits, and make sure to check the baggage rules with your airlines.

How Airlines Measure the Size of Luggage

All airlines have luggage sizers, and all carry-on luggage should fit inside them. You may be asked by the airline personnel to put your backpack inside the sizer. In case it does not fit completely, the bag will be kept in the luggage hold. In most cases, you will have to pay extra fees.

How Strict are the Size and Weight Restrictions on Carry-on Backpacks?

This is very interesting. I have not seen anyone measuring the size and weight of the backpack that was meant to be carried along by the passengers. But I have heard and read a lot of stories where luggage has been rejected as a carry-on and had to be checked-in into the cargo area of the plane. 

I think it depends a lot on the mood of airport personnel. In most cases, they just size the luggage with their eyes and do not say anything if it feels ok to them. It appears they are just concerned whether your luggage will fit in the overhead bin or not. Suitcases and hard cases are more strictly scrutinized. This is because soft cases and backpacks which are usually formless can be squeezed a bit to fit into tiny areas in the luggage bin.

You may specifically find the weight limit of carry-on backpacks very restrictive, especially if you have a lot of electronic gadgets with you. A laptop along with a DSLR camera and a big power bank will make your carry-on backpack heavy, even before you put in your clothes, shoes, or anything else inside the pack. Luckily, almost always they ignore the weight of the carry-on luggage if it looks small enough to fit in the overhead bin.

Most backpacks have external straps to cinch it from the sides. If you think your backpack looks big and may not be allowed as a carry-on, try to cinch it down as much as possible to make it look smaller. People have successfully carried backpacks as large as 60 litres as carry-on luggage. But there is no guarantee that all such attempts will be successful. You should be mentally prepared to shell out extra money if you are planning to take a big backpack as carry-on luggage.

You may be FORCED to Check-in your Carry-on Backpack!

Yes, this can happen even if your backpack is small enough and meet all the size limits of a carry-on. If there is no place to put in your backpack in the overhead bin, you will be asked to put your backpack in the cargo. This usually happens if you are among the last to board the flight. 

This happened to me once while I had a backpack as carry-on luggage. There was absolutely no place in any of the overhead bins to put in my backpack. I asked if I could keep the backpack under the seat in front of me, but they didn’t allow as the backpack was too big for that. I had no option but to let them take away my backpack to be put into the cargo. Luckily, I had a small folding bag inside my backpack. I quickly transferred the laptop and some important documents to the small bag, locked the backpack with a combination lock I had with me, and let them take away the backpack.

I make sure to always carry a small folding bag inside my backpack for such emergency situations. You should also have a TSA approved combination lock in your backpack, and also a rain cover. Usually, luggage is not allowed to be checked-in if they are not locked. Also, if you decide, or forced, to check-in your backpack, putting on a rain cover will save your costly backpack from rough handling and general wear and tear to some extent. If the rain cover gets damaged, you can always get a new one.

How many Carry-on Luggages are allowed?

Only one carry-on luggage is allowed. But some airlines also allow another smaller bag as a ‘personal item’. This can be your purse, a briefcase, or a laptop bag. It should be small enough to fit under the seat in front of you. The weight limit allowed for carry-on luggage may or may not include the weight of the ‘personal item’.

If you are planning to carry a personal item inside the cabin along with your carry-on, always make sure to check the guidelines for cabin baggage beforehand so that there are no last-minute surprises. Also try to board the plane as soon as possible so that you get enough space in the overhead bean to fit both the luggage, as some airlines may not allow keeping anything under the front seat.

Advantages of Travelling Only With a Carry-on Backpack

If you are physically capable of carrying a backpack, there are a lot of advantages of traveling with a carry-on backpack. The most important advantage is the ease with which you can move fast with a backpack, as compared to wheeled luggage or handheld luggage.

carry-on backpack

Wheeled luggage is almost useless in rough roads or in pebbled roads.

Try dragging your luggage for half a kilometer looking for a hotel or accommodation after arriving at a new place, and you will understand what I mean. 

If you love traveling, you will love the flexibility of a backpack specially designed for traveling. A backpack by design is much better suited for carrying heavy loads as compared to suitcases or duffle bags. Also, unlike hiking backpacks that have a top-loading design, travel backpacks open from the sides like a suitcase making it very easy to pack or unpack.

Have you seen how baggage is handled by the airlines? They are literally thrown around from one person to another, or into the carrying van, and then into the flight cargo area. The same process is repeated again after reaching the destination. If you want to save your luggage from the wear and tear of the Baggage Handling System at the airport, the only way is to carry-on your luggage.

A carry-on backpack gives you the option to have the backpack always with you during the entire journey. You minimize the risk of losing your backpack and also save a lot of time as you don’t have to wait at the baggage belts to collect your bags.

Many airlines now charge a fee if you check-in your luggage. If you travel only with a carry-on backpack, you will eventually end up saving a lot of many just by avoiding check-in baggage fees.

Final Thoughts

Traveling with a carry-on backpack is a unique experience in itself. People who love traveling should consider a backpack that can be always carried along with them, no matter what the airline carry-on size restrictions are.

carry-on backpack

Hence it is always advisable to select a backpack that meets the airline size restrictions for carry-on.

It should be easy and comfortable to carry for long durations and has all the extra organizational features that make the backpack easy to pack, unpack, and use. Invest in the right backpack and it will accompany you in many memorable journeys.

About Me

Deb is passionate about pocket tools, bags, and accessories, especially any type of everyday-use gear (or not so everyday-use gear) that makes life efficient, comfortable, and more enjoyable.

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