External Dimensions

What it is

An external dimension is three figures: length, width and depth, describing the box the bag occupies. It is the only specification on this site that a metal frame at a gate can act on, because a frame does not measure volume and does not read liters.

It is also the specification most often replaced with something that looks like it. A case sold as 21 in is not a case that measures 21 inches. Twenty-one inches is a trade size, a naming convention that refers roughly to the height of the body, and the body is not the whole object.

Three of the forty-seven listings gathered here state three figures. The others give a trade size, or a length, or nothing at all.

Why it matters

It decides The Gate Sizer.

Because a frame measures the outermost points of the object you are holding. Wheels add height at the bottom. Feet add width at the side. A fixed side handle adds width again, and a telescoping handle left up adds a great deal of height.

None of the three listings that give a size says whether that size includes the wheels. In this trade it almost never does, which means the published figure is systematically smaller than the object.

The practical consequence is simple: a case whose listing says it matches a published figure exactly is a case that may not, because the two numbers are measuring different things.

What gets written instead

A trade size such as 20 in, 21 in, 22.5 in or 30 in, which describes the body by convention and not by measurement.
The words airline approved or airplane approved, which are printed by the seller and reviewed by nobody.
A single length, as on one duffel that states thirty-four inches with no width or depth beside it.
A capacity in liters, which is a different quantity entirely and cannot be converted into a shape.

The listings that do give it

Every listing below states this figure in its own wording. The other 44 do not, and we have left those blank rather than filling them.

Listing	Category	What it states
LIGHT FLIGHT 20" Expandable Carry-On	Carry-On Luggage	22 x 14 x 9 in
LIGHT FLIGHT 20" Carry-On with TSA Lock	Carry-On Luggage	22 x 14 x 9 in
HOTOR Travel Duffel, 13.4 x 17.3 x 7.9 in	Travel Duffel Bags	13.4 x 17.3 x 7.9 in

A stated size is the size of the body. Wheels, feet and an extended telescoping handle are not usually counted inside it, and the frame at a gate counts all of them.

How to get the number yourself

Stand the bag on the floor, packed as you intend to travel with it, with the telescoping handle pushed all the way down.
Measure height from the floor to the highest fixed point, which means starting at the bottom of the wheels and not at the bottom of the shell.
Measure width and depth across the widest points you can find, including side handles, feet, external pockets and anything else that sticks out.
Write the three figures down and take them with you, then compare them against the figure your carrier publishes for your fare and your aircraft.

Worth being careful about

This site does not print cabin or checked size limits for any airline. Your carrier publishes its own figure and it differs by fare and by aircraft.
Where a listing gives a figure such as 22 x 14 x 9 in, that is the body of the case. Wheels, feet and an extended handle are not usually counted inside it.
A case sold as expandable has two external sizes and only ever states one of them.
A luggage cover adds a layer over the shell, and neither cover listing here states how thick that layer is.