Do airlines really measure the wheels and the handle?

Yes. The sizer at the gate is a box, and the bag either drops into it or it does not, with everything attached. Manufacturers usually quote the case body only, which is why a "22-inch carry-on" can measure 24 inches once castors and a telescopic handle are included. The calculator adds a 4 cm (1.6 in) allowance when you tell it that your measurement left them out.

What is a linear inch, and why do checked bags use it?

Linear size is the three sides added together, so 30 + 20 + 12 in is 62 linear inches. US carriers price checked baggage on that sum rather than on any single side, and 62 in — 158 cm — is the usual line between a normal bag and an oversize fee.

The same case fits one airline and not another. Why?

Because cabin allowances are each carrier's own contract of carriage, not a standard. The IATA "Cabin OK" recommendation of 55 × 40 × 20 cm is a recommendation; an airline is free to be more generous, as several US carriers are with 22 × 14 × 9 in, or stricter, as several European low-cost carriers are with anything beyond a personal item.

My bag is soft-sided. Does that help?

At the sizer, sometimes: a soft case with a half-empty front pocket will compress into a box a hard shell bounces out of. Do not rely on it. If the numbers here put you over on the longest side, you are relying on the gate agent's mood, and the fee for being wrong is charged at the aircraft door.

Carry-on size calculator

A 22 × 14 × 9 in case measured without its wheels and handle is 46.9 in around the three sides, which is 1.6 in over what United allows in the cabin. The airline measures the whole bag; the tape in your hand usually does not.

Result+1.6 in

It is 1.6 in (3.9 cm) over what United Airlines allows on at least one side.

The same bag still fits: Southwest Airlines, Frontier Airlines.
You measured without the wheels and the handle, so 1.6 in (4 cm) was added to the longest side — that is the side the gate sizer catches.

Trip Card

This trip only: the numbers it produced, the limits and tariffs it was checked against, and when those were checked. Print it or send it to whoever is travelling with you.

Your bag, as the sizer sees it	23.6 × 14 × 9 in
Linear size (three sides added)	46.9 in
This carrier allows	22 × 13.8 × 8.7 in

Sources: united.com/en/us/fly/baggage/carry-on-bags (checked September 19, 2026) — not verified yet — check with the carrier or the road operator

Trip Card generated on September 20, 2026

What the calculator measures

Three numbers go in — the longest side, the width and the depth — plus the airline and what kind of bag it is: a personal item that goes under the seat, a carry-on for the overhead bin, or a checked bag.

Two things then happen that a printed allowance cannot do for you.

First, the sides are sorted. A sizer does not care which side you called the length; it cares that the largest dimension of the bag fits the largest dimension of the box. Second, if you say the wheels and the retracted handle were not in your measurement, an allowance is added to the longest side, because that is where castors and a handle actually sit and that is the side the sizer catches.

Why it answers with “over by”, not “no”

“No” is not useful at eleven at night with a bag half packed. The number of centimetres, or inches, that you are over tells you whether the answer is repacking the front pocket or buying a different case.

Where the bag does not fit, the tool also lists the carriers whose published cabin allowance it still clears. A case that misses a 56 × 35 × 22 cm sizer by an inch and a half is a perfectly legal carry-on on airlines with a 61 × 41 × 25 cm limit — and on a US domestic route you often have a choice of both.

Weight, where it applies

Most US carriers do not weigh cabin bags; several European and almost all Asian carriers do. Enter a weight if you have one and the check runs; leave it empty and the tool checks size alone rather than inventing a limit. The same rule applies to every figure here: where an allowance has not been verified against the carrier’s own page, it is marked rather than presented as fact.

What this means in United States

US carriers rarely weigh a carry-on, but they do check the sizer at the gate, and the numbers in inches are not a rounded version of the European ones: 22 × 14 × 9 in is 56 × 36 × 23 cm. Checked bags are governed by the 62 linear inch (158 cm) sum of the three sides, and one inch over moves the bag into the oversize fee.

Questions people actually ask

Do airlines really measure the wheels and the handle?: Yes. The sizer at the gate is a box, and the bag either drops into it or it does not, with everything attached. Manufacturers usually quote the case body only, which is why a "22-inch carry-on" can measure 24 inches once castors and a telescopic handle are included. The calculator adds a 4 cm (1.6 in) allowance when you tell it that your measurement left them out.
What is a linear inch, and why do checked bags use it?: Linear size is the three sides added together, so 30 + 20 + 12 in is 62 linear inches. US carriers price checked baggage on that sum rather than on any single side, and 62 in — 158 cm — is the usual line between a normal bag and an oversize fee.
The same case fits one airline and not another. Why?: Because cabin allowances are each carrier's own contract of carriage, not a standard. The IATA "Cabin OK" recommendation of 55 × 40 × 20 cm is a recommendation; an airline is free to be more generous, as several US carriers are with 22 × 14 × 9 in, or stricter, as several European low-cost carriers are with anything beyond a personal item.
My bag is soft-sided. Does that help?: At the sizer, sometimes: a soft case with a half-empty front pocket will compress into a box a hard shell bounces out of. Do not rely on it. If the numbers here put you over on the longest side, you are relying on the gate agent's mood, and the fee for being wrong is charged at the aircraft door.

Where these numbers come from

Last checked: September 19, 2026

United Airlines — carry-on baggage — September 19, 2026
IATA Cabin OK recommended cabin bag size — September 19, 2026

In the United States baggage allowances are the carrier's own contract of carriage; the Department of Transportation requires the fees to be published, not harmonised, so two airlines on the same route can measure the same suitcase differently.

These figures are guidance, not a quotation. Airline allowances, gate fees and toll tariffs change; check the carrier or the road operator before you travel.