How To Calculate Linear Inches

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Every now and then an airline will tell you the maximum size of luggage you can take and use the phrase “linear inches”.

They sometimes do this when talking about carry-on luggage, you might see an airline say… your carry-on bag can be 45 linear inches.

More frequently they use “linear inches” when talking about checked bags and often they’ll say… your checked luggage must not exceed 62 linear inches.

This can be a little confusing because “linear inches” is not an expression that you normally hear anywhere else in life.

The airlines are speaking their own language and we, the passengers, are just supposed to figure out what they mean!

This post tells you what they mean and how to calculate linear inches so you know if your suitcase is going to be allowed or not.

How To Figure Linear Inches

Maybe you are thinking… I know what a regular inch is… but heck… what is a linear inch?

Don’t worry an inch is an inch, they are not a different size or anything like that. The meaning of “linear inches” is really quite simple.

All suitcases have a length, width, and height. They are 3 dimensional. Stores or manufacturers will tell you the dimensions of a suitcase or you can take a regular tape measure and measure and write down the 3 dimensions of your suitcase.

To figure the linear inches of a suitcase you simply take those 3 numbers, length, width, and height and sum them together.

Linear Inches = length + width + height

So if a suitcase has height 22 inches, Width 14 inches, and height 9 inches you figure 22 + 14 +9 = 45 inches

So a 22 x 14 x 9 inch suitcase is called 45 linear inches. That’s typical for carry-on luggage airline restrictions.

For checked luggage, the most common size limit in the united states is 62 linear inches. Allegiant allows a larger checked suitcase that is 80 linear inches.

Even though it’s annoying for passengers to figure it can be quite handy sometimes.

If the airlines set the luggage size restrictions with linear inches it means 1 dimension can be a little longer so long as another dimension is a little shorter.

Let’s look at some suitcases:

Travelpro Maxlite 5-Softside

This case is 28 x 19 x 11 inches. So when we sum those 3 numbers together we get 58.

So this TravelPro case is 58 linear inches and good to go for checked luggage.

AmazonBasics Softside Spinner Luggage Suitcase

This AmazonBasics case is 30.9 x 17.5 x 12.9 inches.

When we add these numbers together we get 61.3 linear inches.

So again this case is under 62 linear inches.

AmazonBasics Large Nylon Duffel Bag

This large duffel bag is 32.5 x 17 x 11.5 inches.

When you add them together you get 61 linear inches.

Again it’s under 62 linear inches and will be fine to be checked.

FAQ’s

How big is 62 linear inches?

Not all bags that are 62 linear inches have the same volume capacity.

Imagine someone is packing a fishing rod in a box. Let’s say it is 2 x 2 x 58 inches.

We add 58 +2 +2 and can see that the airline industry would describe the box as 62 linear inches.

But if we multiply the dimensions 58 x 2 x 2 we can see that the volume capacity of the box would be only 232 cubic inches (about 3.8 liters). Although it’s long the fishing rod case is not taking up a lot of space.

Let’s look again at the TravelPro Maxlite from above:

Its dimensions are 28 x 19 x 11. By multiplying those three numbers we can calculate that its volume capacity is 5852 cubic inches (about 95.9 liters). That’s a lot more than the fishing rod box!

So what’s the largest 62 linear inches box that you could take as your checked luggage?

That would be a perfect cube 20.66 x 20.66 x 20.66 inches. It would have a volume capacity of 8818 cubic inches (about 144.5 liters).

Wow a 62 linear inch cube has a lot more space than a regular suitcase shaped box!

This makes me curious why luggage makers don’t make suitcases that are shaped like cubes. I guess they would just not be the most practical shape even if they could fit more stuff.

Does the 62 linear inches include wheels?

Good question!

The answer depends to an extent on who you are flying with and which individual measures your bag. I took a look at Twitter to try to get you answers.

American Air

Mark was worried that when included the wheels and added the 3 linear dimensions of his spinner suitcase it was just over 62 inches in total.

American Air told him that they didn’t include the wheels when measuring checked luggage.

But this was a surprising result so I checked again.

This time they told Ben that wheels are included in the measurement…

And the told Julie it depends of the wheels protrude… as if wheels don’t always protrude…

Basically American Airlines or at least the Twitter social media team don’t really know. They give a different answer every time they are asked.

Ultimately it will come down to the mood of the check-in agent who measures your luggage.

Delta Airlines

Delta takes a different approach and does include the wheels:

Frontier

Here is Frontier telling Kevin that his bag that is half an inch over 62 inches might not be accepted because of the wheels!

And look at that $75 fee for an oversized bag… ouch!

JetBlue

JetBlue also counts the wheels and the handles when measuring luggage.

Southwest Airlines

Southwest also count the wheels when measuring linear inches:

And again that’s hefty $75 penalty if your sticking out wheel takes you over 62 linear inches.

Spirit Airlines

Spirit also will charge you if a protruding wheel or handles takes you over 62 linear inches.

And take note their weight limit of 40 pounds is less than most other airlines which usually allow 50 lbs per checked bag.

United Airlines

United count the wheels and handles as part of the 62 inches too.

The simple answer is that when you are measuring your own luggage do include the wheels and the handles. That way you don’t get any nasty surprises by airlines trying to mug you for extra cash when you check your baggage.

How many linear inches is a 29 inch suitcase?

Hopefully, by now, you’ll understand that you need all 3 dimensions to calculate the linear inches of a suitcase. A 29-inch high suitcase could have many different lengths and widths and hence many different values for linear inches.

Add length + height + width to calculate the linear inches.

The Verdict

The airline industry uses this linear inches luggage measurement for a reason.

When you are packing carry on luggage into the overhead bin or underneath your seat it really needs to be the correct shape for all the bags to pack efficiently.

With checked luggage, it’s not so important that all bags have the same shape because checked luggage is going in the cargo section of the plane. By using linear inches it allows passengers to bring all different shapes of luggage but still puts an upper limit on the size.

So next time you are scratching your head trying to figure out the linear inches remember that it’s actually a handy thing that lets passengers bring luggage of all different shapes.

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