This article is meant to clarify some confusion between luggage sizes that are advertised by manufacturers vs. what airlines limit. In general, as long as you are close to the airline’s requirements, then you’ll probably be fine. However, it depends on the airline, and ultimately the gate attendant has the final call. Budget airlines, like Allegiant, tend to be stricter on their carry-on regulations.


Variability in Advertised Sizes

It’s to the benefit of each luggage manufacturer to be within the size requirements of as many airlines as possible. Because of this, some manufacturers may shave off an inch, or choose not to include the handles or wheels in their measurements, which certain airlines may take into consideration. 

To complicate the issue, some airlines advertise internal dimensions, outer dimensions, and overall dimensions. With three different measurements and varying size requirements across each airline, the discussion becomes complicated. 

varying luggage dimensions

To be clear, any of the reviews I do on this website; I include measurements that I have personally taken. I measure the longest side of any dimension, so if the bag is an odd shape, like the trapezoid-like shape of the TravelPro Maxlite 5, you know you have the max measurement. 

I take the measurements from the wheels up and include any handles, locks, or other outer components airlines will usually count. 

Be aware that if a carry-on can expand, that is not taken into consideration and not advertised here or anywhere else. This is due to the variability introduced. Some people may be able to close theirs, but with a bulge in the middle of the bag. Others may not.


What Airlines will Accept

Here’s the deal, unless your bag is blatantly not compliant, for example - bringing a large checked bag to the gate, you’ll probably be alright even if it’s only an inch or two larger on one side or another. Just make sure you’re not overpacked, and your out-of-spec bag is not bulging at the seams.

For my reviews, this is reflected in the compatibility tables. Green checks indicate a bag is close and you’ll be alright more often than not. Yellow caution triangles indicate it may draw attention, especially if compared to other bags. Red hexagons means that you’ll have a low chance of getting it on the plane. 

Most gate attendants don’t want to deal with having to check your luggage in, deal with the fuss, and slow down the boarding process. 

That being said, some budget airlines will be more strict on their policies. For all airlines, there is not a significant margin on flights, let alone the cheaper budget-friendly airlines. These airlines may be more prone to checking and requiring you to pay to have it checked if your bag doesn’t fit in the metal frame. 


International Flights vs. Domestic

Somewhere in a cubicle in a large city, there’s some guy or gal that had to calculate the estimated annual cost savings for reducing the allowable carry-on size for international flights. God bless their soul. 

International flights typically have slightly smaller allowable sizes than domestic US flights. This varies greatly, so check with your respective airline. 

The big thing to watch out for with an international flight is the weight limit. Weight limits for carry-on luggage are typically much smaller than domestic flights, depending on the airline. 

You’ll see some carry-ons advertised as specifically for international flights. These bags are smaller in size, meant to meet more size requirements than their domestic counterparts. 


Personal Items 

For most airlines, you are also allowed to bring a ‘personal item’ on the plane, along with your carry-on. Most people carry a purse, backpack, briefcase, diaper bag, or something of the like. This cannot be another full-size carry-on. As the name implies, it’s supposed to be a smaller bag that will fit under the seat in front of you. 

Sometimes you can get away with bringing a plastic bag in addition to your personal item if you bought it after passing through security. This depends entirely on the gate attendant. Some will say something; others won’t care. 


What are Linear Inches?

You may also see some airlines advertise the allowable carry-on as a ‘linear inches’ or ‘linear centimeters’ measurement. What this means is your carry-on must not exceed a certain threshold when you add up the length, width, and depth of your carry-on. 

For example, the Chester Minima Carry-On measures 21.5” in length, by 13.5” in height, and 8.75” in depth. Add up [21.5 + 13.5 + 8.75], and you get 43.75 inches. This carry-on measures 43.75 linear inches. It works the same way for centimeters. 


How to Measure Carry-On Luggage

If you’re unsure of whether your bag is allowed, set your bag on a flat surface and grab a measuring tape. 

You will take measurements across the length, width, depth of the bag at the largest points. Most bags are rectangular prisms; however, some have less-common shapes, and you’ll need to find the longest point on each plane. 

Be sure to include the handles, wheels, and any other components. You do not need to extend the handle as long as it retracts into the bag.

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