Is a 40L Backpack Carry On Size? Find Out Here! 

 June 27, 2023

By  Keith Terrell

As convenient and easy as air travel has become in the modern world, packing the right carry-on size can often be a challenge. Airlines have strict guidelines for carry-on bags, and if you don't meet those guidelines, you have to pay a hefty checked baggage fee and experience additional stress. So if you're wondering, is a 40L backpack carry-on size? The answer, of course, depends on the airline and the type of bag.

Generally, a 40L backpack is considered a carry-on size by most airlines. However, please check the respective airline's guidelines regarding the size and quantity of your

In this blog post, we'll go over all the factors that determine whether a 40L backpack is considered carry-on and how you can avoid any costly checked baggage fees on your next flight. Read on to find out the answers to all your questions about the 40L backpack carry-on size.

How to Measure a Backpack for Carry-On

When it comes to packing for a flight, it can be difficult to know what to bring and what backpack size you can take with you as carry-on luggage. Fortunately, there are a few simple steps you can take to measure a backpack according to the criteria for carry-on:

First, it is important to measure the length and width of your backpack. This will help you determine if your backpack meets the carry-on requirements of most airlines. When measuring the length, start at the top and then measure to the bottom of the backpack. For width, measure along the widest point of your bag.

Once you've measured both, add these numbers together. If they end up being over 45 inches, then unfortunately your bag won't qualify as a carry-on item. However, keep in mind that many airlines also accept individual items (e.g. laptops and small bags) that exceed the hand luggage dimensions, as long as they do not exceed the overall dimensions.

Although some travelers may be tempted to solve this problem by stuffing their backpack as much as possible, you should be aware that a bag that is too tight or too stuffed can also significantly increase its dimensions that it will no longer be accepted as carry-on luggage. It's always better to opt for two pieces of luggage instead as everything should fit in without risking trouble with the airline staff or lack of space.

Knowing exactly how to measure a backpack for carry-on is essential when deciding on which items we can take with us on our travels. The next section is about measuring the individual dimensions and which backpack size is actually suitable as carry-on.

Measuring Dimensions

When measuring a backpack for carry-on size regulations, it is important that you consider the dimensions of your bag as well as its capacity in terms of liters. As far as dimensions go, the most important aspect is to ensure that the linear inch measurement of your bag does not exceed the allowable limitations, e.g, 22 x 14 x 9 inches (56 x 36 x 23 cm) for most airlines. Anything over this is considered too large for a checked bag and must then either be packed in a larger suitcase or carried as checked baggage.

Interestingly, some airlines allow variations of these sizes with slightly larger dimensions than those specified. American Airlines, for example, allows luggage up to 24 x 16 x 10 inches (61 x 41 x 25 cm) as long as it fits in the overhead compartment. This would make it possible to carry a 40L backpack on board if it is within these dimensions. However, even if airlines allow larger pieces of luggage, passengers should pay close attention when measuring their suticases as cabin crew has the final decision on whether they are allowed on board.

Even though there are guidelines that specify maximum dimensions and weights, you should play it safe and measure the dimensions of your luggage before entering the terminal to avoid unnecessary delays at security checks and boarding! It is therefore important to know the airlines' regulations regarding size restrictions in order to decide whether you can take a 40L backpack as a carry-on item.

To better illustrate these requirements, let us now analyze which airlines are particularly lenient in allowing carry-on luggage.

What Airlines Allow Carry-On Luggage?

When it comes to which airlines allow carry-on luggage, the answer can be complex. Choosing the appropriate size depends not only on your airline’s policies, but also on laws enacted by the federal government. Airlines typically assess their carry-on policies based on outside dimensions and linear inch measurements — that is, when you add up the length, width, and height of your bag.

For instance, on some U.S. airlines, a carry-on bag cannot be larger than 45 linear inches, while others require that all personal items must fit under the seat in front you without protruding into the aisles or obstructing other passengers.

Despite these restrictions, 40L is considered a guideline for domestic flights, on both large and small airlines. Some airlines reserve the right to enforce it more strictly, such as if cabin space is limited. However, as long as everything fits in your 40L backpack, you will probably still qualify with the requirements for personal items.

Whether or not a 40L backpack is considered an acceptable carry-on size depends on the airline policies and whether or not your specific measurements meet their standards. Now that we've discussed dimensions, let's look at the differences in international airline regulations and how they can affect packing for overseas destinations.

  • The International Air Transport Association (IATA) states that the maximum dimensions for a standard carry-on bag are 22 x 18 x 10 inches (56 x 45 x 25 cm).
  • IATA has noted that certain airlines may have restrictions on the weight of carry-on bags, with some starting at around 5kg (11lbs).

International Airlines Regulations

If you are traveling abroad on an international airline, size regulations may vary compared to domestic airlines. Depending on the airline, backpacks with a capacity of more than 40L are allowed as hand luggage, while other airlines have specific rules that require all luggage to comply with the maximum size allowed.

On the one hand, it is beneficial for travelers to be less strict about the size of their luggage. This allows them to pack more items without worrying about having an oversized backpack. This also benefits those who prefer to travel light and compact but still need to bring a few items.

On the other hand, allowing luggage of any size could lead to overcrowding and excessive storage by passengers trying to take advantage of this leniency. Overstuffed overhead bins can be dangerous in many ways, leading to water damage to passengers and flight attendants if heavy items are not secured during turbulence.

It is always best to check with your airline prior to flying to ensure that your complies with size regulations. Knowing exactly what the airline's guidelines are will save you time at security and make your overall flight experience smoother and more enjoyable. Then you can plan what type and size of luggage will both suit your needs and meet international airline standards.

In the next section, you will learn how to find out if your baggage complies with the limits and how to be prepared for your trip.

How to Tell if Your Bag is Within the Allowed Sizes

When it comes to determining whether or not a 40L backpack qualifies as carry-on luggage, travelers first need to know the regulations of the international airline they are flying with. International airlines may differ in their size restrictions for domestic and international flights. While some may specify a maximum size limit of 22 x 14 x 9 inches (56 x 36 x 23 cm), others could require bags to be less than 18 x 14 x 8 inches (45 x 35 x 20 cm). It is important to check the size requirements on each airline's website before packing your luggage.

If you want to take a 40L backpack as carry-on luggage, you should also bear in mind that the above measurements do not take into account the length of the straps or wheels, which may extend beyond the actual backpack. This can result in even an otherwise acceptable bag being rejected as too large if the length of the straps or the width of the wheels are not taken into account in the measurement. There are also weight restrictions on carry-on luggage for international travel, usually starting at 8 kilograms (18lbs).

To determine if a 40L backpack is allowed as a carry-on, you should visit the international airline's website before departure, look at the maximum allowable dimensions, and consider how much padding such as straps and wheels contribute to the overall size of the bag. From there, estimating the total weight is crucial to being able to board your flight without any problems!

Familiarizing yourself with the regulations on the size and weight of your luggage will help you calculate dimensions and volume to ensure that you choose the most suitable piece of luggage for your trip.

Calculating Dimensions and Volume

When calculating whether the size of your backpack meets airline requirements for carry-on, it is important to consider both dimensions and volume. Let's take a look at the differences between them.

Dimensions refer to length, width, and height. They determine how much space your luggage will take up in the aircraft cabin. For example, most airlines stipulate that a carry-on luggage should not exceed 22 inches in length, 14 inches in width, and 9 inches in height. To ensure this, measure your luggage as accurately as possible with a tape measure or ruler.

Volume gives you an indication of how much your backpack can hold. It refers to the physical capacity of your bag and is usually expressed in liters (L). For example, the maximum allowed volume of a carry-on bag can range from 16L to 45L depending on which airline you are flying with. Volumes over 45L will likely not be allowed as they exceed airline guidelines.

While there is some debate over what size and shape bags qualify as a carry-on, it seems reasonable to assume that any bag with a combined external dimensions of less than 22 x 14 x 9 inches (56 x 36 x 23 cm) should fit within most airline guidelines for a personal item or underseat storage. Furthermore, bags with a total volume of 40 L or less should also generally meet airline restrictions for cabin luggage dimensions and weight allowances.

When choosing the size of an airline carry-on backpack, it is important to consider both dimensions (length, width, and height) and volume. Different airlines have their own requirements, but in general, bags with dimensions up to 22 x 14 x 9 inches (56 x 36 x 23 cm) and  a volume of 40L should be allowed on most airlines. To ensure your bag meets these criteria, it is best to measure it accurately with a tape measure or ruler.

Frequently Asked Questions

How does the size of a 40L backpack compare to the maximum size allowed for carry-on luggage?

A 40L backpack is actually slightly smaller than the maximum size for a carry-on bag. Most airlines have a maximum carry-on capacity of about 45L, so the 40L backpack would be about 5L or 1/9 cubic feet (11.3%) smaller than the maximum allowable carry-on volume.

However, it's important to note that size restrictions can vary from airline to airline, so it's best to check with your airline before traveling to confirm if your bag meets the requirements.

Is there a way to measure whether a 40L backpack meets the carry-on size requirements?

Yes, there is a way to measure whether a 40L backpack meets the carry-on size requirements. Generally, airlines allow passengers to carry a piece of luggage no larger than 22 inches long, 14 inches wide, and 9 inches deep. Additionally, the total linear dimensions (length + width + height) should not exceed 45 inches.

If your 40L backpack falls within these dimensions, then it is allowed as a carry-on bag! Check with the respective airline for specific regulations as most airlines have different carry-on size requirements.

What are the regulations for carry-on luggage in the airline I'm flying?

The regulations for carry-on luggage vary from airline to airline, so it's important to check the specific guidelines of your chosen airline before you fly. In general, most airlines allow passengers to bring one piece of carry-on luggage and one personal item, such as a purse or laptop bag, on board.

The carry-on bag must fit comfortably in the overhead compartment or under the seat in front of you, which usually requires a maximum bag size of 45 linear inches (width + length + height). Additionally, many airlines limit the weight of carry-on luggage to around 25 pounds. Be sure to double-check with your airline as these requirements may change from time to time.

About the author

Keith is a one bag traveler and the owner of Backpacks Global. His go to backpack is the Osprey FarPoint 40.

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