Cabin baggage: size, weight and the personal-item trap

The two pieces to keep separate

Almost every carrier distinguishes the cabin bag, which goes in the overhead bin, from the personal item, which goes under the seat in front of you. They are two different things with two different rules, and that is where the bill is decided.

On a full-service carrier both are normally included in the base fare. On a very low-cost carrier, often only the personal item is included, and the cabin bag becomes a paid extra, sometimes more expensive than a checked suitcase would have been.

That is the main reason a fare advertised $90 cheaper ends up costing more. The displayed price does not include the same things on both sides.

The dimensions to remember

The most widespread cabin bag format sits around 55 x 40 x 23 cm, wheels and handles included. That last detail is what catches people: a suitcase advertised as compliant often measures a few centimetres more once the wheels are counted.

The personal item is much smaller, roughly 40 x 30 x 15 cm depending on the carrier. An everyday backpack generally passes, a hiking pack does not.

Weight varies far more than dimensions. Some carriers never weigh cabin bags, others impose a strict limit around 10 kg and enforce it at the gate. Check the baggage page of the exact carrier you are flying, not the group it belongs to.

Sizers, and the moment it gets decided

The metal sizers near counters and gates are not decorative. When a flight is full, staff use them, and the fee paid at the gate is almost always higher than the same extra bought online at booking.

The worst case is being stopped at boarding: you pay the highest rate, your bag goes to the hold, and you collect it at the carousel after organising your whole trip to avoid exactly that.

If your bag is borderline, buy the allowance in advance. It costs less, and it settles the question before it comes up.

What usually does not count

Several items travel on top of your two allowed pieces, which helps when you are tight.

• A coat : It does not count as baggage. Wearing your bulkiest coat rather than packing it frees a lot of space in winter.
• Baby equipment : Strollers and car seats normally travel free, on top of your allowance, and are checked at the gate.
• Mobility aids : A cane, crutches or a wheelchair never count toward your allowance.
• Duty-free purchases : A sealed bag bought after security is usually accepted on top, but not everywhere. On a connecting flight, check before you buy.

Comparing two fares properly

Before comparing, decide what you are taking. If you are going for a week with a cabin suitcase, add the round-trip cabin fee to each carrier fare, then compare the totals.

On a round trip, a $45 fee each way adds $90 per person. For two people that is $180, which completely reorders two fares that looked close.

It is the same habit as with seat selection: the advertised price is a starting point, not the price of the trip.