The largest bag you can check on most US airlines is described as “62 linear inches”.

It’s pretty much the standard maximum size of a large checked suitcase, only Allegiant is more generous with 80 linear inches.

That word “linear” is important.

They don’t mean a bag that is 62 inches high!

To calculate linear inches you need to **sum **the length + width + height of your suitcase.

So long as the sum of these three measurements is less than 62 inches your suitcase will not be oversized.

So what is the biggest bag you can check on a plane? And what if your bag is a little too big.

To calculate the volume of a rectangle you need to **multiply **the length x width x height.

Time for some math!

## The Largest Size Checked Suitcase Allowed on US Airlines

On paper, the largest luggage size for check in is cube-shaped and is 20.66 x 20.66 x 20.66 inches.

A bag of these dimensions would be exactly 62 linear inches and have a capacity of a whopping **144 liters**.

A more conventionally shaped large checked suitcase is usually around 29 inches tall.

It might be something like 29 x 22 x 11 inches. It’s 62 linear inches too, but a bag that shape would only be **115 liters**.

Because 29 x 22 x 11 is 7018 cubic inches. Or 115 liters.

Or imagine a taller bag that is 33 x 20 x 9 inches. Again, that’s 62 linear inches.

You’d think that the 33 inch case would be larger than the 29 inch case right?

But no…

33 x 20 x 9 = 5940 cubic inches. Or **97 liters**.

The further away you get from the perfect cube the less space there will be inside the case.

In practice, nobody sells luggage in the largest permitted size because cubes make impractical luggage.

Most luggage is rectangular and flatter, and this means that the capacity is reduced vs the theoretical maximum.

## So How Big Is A 62 Inch Suitcase?

So now you know the answer is… it depends…

The capacity of a 62 linear inch suitcase varies depending on how “boxy” the three dimensions are.

Consider this AmazonBasics suitcase:

It’s dimensions are 32.2 x 20.6 x 12.2 inches.

If we sum those three numbers it’s 65 linear inches.

**Hang on a second… that’s too large!**

Yes, in the strictest sense, the AmazonBasics suitcase is too big to be checked in with all the main US airlines.

The airlines set the rules. The luggage manufacturers stretch and bend the rules. But it’s you, the passenger, that will pay the fine if some antsy check in agent pulls out his measuring tape.

Read all the reviews though and you’ll see that nobody is complaining about it being too large. So what’s going on…

Well, in theory, the limit is 62 linear inches…

And the wheels and handles do count when measuring.

But, in practice, the airline check-in agents must employ a little common sense. They must have some leeway otherwise there would be outrage in the reviews.

## Is 32, 29, or 28 Inch Luggage Considered Oversized?

It’s clear then that when only considering the height of a suitcase it’s impossible to know if it’s oversized.

You must also check the width and depth. Sum the three dimensions to see if they are less than 62.

I do understand that all this is probably very frustrating but hey… I don’t make the rules!

So what size should you buy to give yourself the most capacity?

## Don’t Forget About Weight Restrictions

Most airlines only allow 50 pounds maximum weight and they can be very strict with weight limits.

It’s always best to weight your luggage before you go the the airport to avoid nasty surprises.

Searching for a perfect cuboid suitcase to take as much as possible might be pointless.

If you filled a 144 liter cube suitcase it would probably be over the weight limit.

My best advice is to buy a suitcase that is close to 62 linear inches. Most cases advertised as checked large size with height around 29 inches will add up to be more than 62.

If you do the math and it’s slightly over 62, check all the reviews to see if anyone is reporting problems with the size of the bag.

Think about the type of airline that you tend to fly with…

Full-service airlines will be unlikely to try to penalize you for a protruding wheel or handle.

But I wouldn’t be surprised if budget airlines try to squeeze every last dollar out of you.

The cheaper your ticket the more likely the airline will be to try to sting you some other way.

If you are risk averse then look at medium checked suitcase with will be around 25 inches tall. They will have much less capacity but will definitely be under the 62 linear inch rule.

## The Verdict

This is more complicated than you thought right?

Using linear inches allows a degree of flexibility while still imposing limits.

It allows airlines to accommodate oddly shaped items as checked luggage.

But it’s quite confusing for passengers and makes it hard for us to know our maximum baggage allowance.

The takeaway is…

The largest suitcase that you *can *bring is unlikely to be the suitcase that you want to bring.

Learning math in school wasn’t a complete waste of time!

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