Carry-on or checked baggage: how to decide before you book

Baggage is the most common way a flight ends up costing more than expected. The fare looks competitive, then a bag is added at checkout, or worse, at the airport where the rates are highest.

The rules genuinely differ by airline, by route and by fare type, so this is a guide to how to check rather than a list of allowances that would be wrong for someone.

Allowances are set by your fare, not just your airline

The same airline can give you a generous allowance on one ticket and none at all on another. What decides it:

• The fare type. Basic, light and similar fares often exclude checked bags entirely.
• The route. Long-haul allowances are frequently more generous than short-haul.
• The cabin. Premium cabins usually include more.
• Your status, if you hold frequent-flyer status with the airline or its alliance.

This is why "how much baggage do I get" has no single answer. Check the fare in front of you.

Two systems, and they are not interchangeable

Checked baggage is sold either by piece or by weight:

• Piece system: you get a number of bags, each with its own maximum weight.
• Weight system: you get a total allowance and can distribute it across bags.

Mixing them up is a classic and expensive mistake, particularly on itineraries where different airlines operate different legs. Which system applies is stated in your fare rules.

Cabin bags have limits too

Cabin baggage is not a free-for-all. Airlines set both size and weight limits, and on busier routes they enforce them. Two things worth knowing:

• A "personal item" — a small bag that fits under the seat — is often allowed in addition to a cabin bag, but on the most restrictive fares it may be all you get.
• A cabin bag that fits one airline's sizer may not fit another's. On a multi-airline itinerary, the strictest limit is the one that matters.

When to pay for a checked bag

Pay in advance if:

• you are travelling for more than a few days
• you need liquids over the cabin limit
• you are bringing gifts, equipment or anything bulky
• you are travelling with children, whose things add up faster than you expect

Buy it when you book, or at least online before you travel. Airport baggage charges are almost always the highest rate the airline offers, and paying them is entirely avoidable.

When carry-on only genuinely works

Cabin-only is a real saving on short trips, and it has a second benefit people forget: you cannot lose a bag that never left your side, and you walk straight out on arrival.

It works well when you are away for a few days, staying somewhere with laundry, and not carrying anything bulky.

Before you pay, check these four things

1. How many bags your fare includes, if any.
2. Whether it is a piece or weight allowance.
3. The cabin bag size and weight limit.
4. Whether every leg of the itinerary has the same rules.

If any of those is unclear on the fare you are looking at, find out before booking rather than after. Our FAQ covers the common cases, and you can always contact us about a specific itinerary.