How to Measure Luggage

1. Empty the bag and stand it upright. Measure the bag as it will be presented at the gate: upright on its wheels, on a flat floor, with any expansion zip closed.
2. Measure height from the floor to the top of the retracted handle. Include the wheels and the handle housing. This is the number manufacturers most often understate, because their 'case' dimension excludes both.
3. Measure width at the widest point. Measure across the face of the bag at its widest, including side handles, external pockets and any protruding trim.
4. Measure depth at the thickest point. Measure front to back at the thickest point, including wheel housings and any front pocket. Depth is the dimension a soft bag loses first when packed.
5. Add the three figures for linear inches. Height plus width plus depth is the linear-inch figure. Delta caps carry-ons at 45 linear inches, and most US carriers cap checked bags at 62.

Why the number on the box is the wrong number

Luggage makers routinely publish two sets of dimensions and label them differently. Travelpro, for example, publishes both a case size and an overall size for the same bag: the Maxlite 5 carry-on is listed at 21 × 14 × 9 in as a case and 23 × 14.5 × 9 in overall. Both figures are true. Only the second one is what a gate agent measures, and it is 2 in taller than the first.

This is not a trick unique to one brand. The convention across the industry is that “case dimensions” describe the shell and “overall dimensions” add the wheels and the handle housing. Retail listings and product names almost always quote the smaller one, because “21-inch carry-on” sells better than “23-inch carry-on that is over the limit at six US airlines”.

American Airlines states explicitly that it measures the full outside size of a carry-on including wheels and handles. Allegiant goes further and states that the measurement includes wheels, pockets, handles and decorations. Assume every carrier means the same thing, because at a sizer they do.

What you need

• A tape measure. A rigid one is easier against a bag’s curved shell than a soft tailor’s tape.
• A flat floor and a wall. Standing the bag against a wall gives you a square reference for the height measurement.
• Nothing else. A phone measuring app will get you within an inch, which is not good enough when the margin between passing and being gate-checked is often half an inch.

The three measurements, in detail

Height. Floor to the very top of the bag with the telescoping handle pushed all the way down. On most wheeled cases this includes both the wheel diameter at the bottom and the raised handle housing at the top, and together those add 1.5–2 in over the shell height.

Width. Across the face at the widest point. On hardside cases this is usually the middle of the shell where it bulges most; on softside cases it is often the side handle or an external pocket. Measure with the bag empty — a packed softside case gets wider, and the sizer does not care that it was narrower this morning.

Depth. Front to back at the thickest point, including the wheel housings that stand proud of the shell and any front pocket. This is the dimension that most often disqualifies a soft bag, because it is the dimension that grows most when you overpack.

Linear inches, worked

Linear inches is simply height plus width plus depth. It exists because a bag can satisfy three individual maxima and still be an awkward shape, and because it is a single number a handler can apply quickly.

The checked-bag equivalent is 62 linear inches, which is the near-universal US standard, usually paired with a 50 lb weight cap. The same measuring method applies — wheels and handles included.

Measuring a soft bag honestly

A hardshell case is the size it says it is. A backpack or duffel is the size of whatever is inside it, which makes the published figure a floor rather than a fact. If you are measuring a soft bag to decide whether it will pass:

1. Pack it the way you actually pack it, not empty and not stuffed for a photo.
2. Do up every compression strap the bag has.
3. Measure depth last and measure it at the fattest point, which on a loaded pack is usually two-thirds of the way up.
4. Leave yourself half an inch of margin on every dimension. A soft bag that measures exactly at the limit will not measure exactly at the limit on the return leg with souvenirs in it.