1. Limits vary by route, cabin and fare
The same airline can allow a different checked-bag weight in economy and business, or on a long-haul flight and a short regional one. The fare class, not the airline name, usually decides the allowance.
Low-cost fares increasingly charge per bag even on short flights. The booking confirmation lists the allowance for each leg, so check it before packing.
2. Size is measured in linear or three dimensions
Many airlines state a maximum of 158 cm linear (length + width + height) for checked bags, with a weight cap of 20–23 kg in economy. Others give exact dimensions.
Measure the bag including wheels and handles. A soft bag that compresses can change its dimensions, so measure it as packed.
3. Weight classes and excess fees
Common economy allowances are 20 kg, 23 kg or 30 kg per bag; excess weight is charged per kilogram or per extra bag. The fee at the airport is usually higher than when paid online.
If you are close to the limit, move heavier items to your carry-on or a personal item—but check the carry-on limit first, since it is usually much smaller.
4. Special items
Sporting equipment, musical instruments, fragile items and strollers are usually handled separately from normal luggage and may need pre-approval or an extra fee.
Packing fragile items in the middle of a bag with soft layers on every side is safer than relying on the printed fragile label alone.
5. Common mistakes
Common mistakes include measuring the empty bag, weighing only the contents, ignoring the per-leg allowance on multi-city bookings, and assuming the allowance follows the airline brand rather than the fare.
Another is packing liquids over the carry-on limit and being forced to check the bag at the gate, where fees are highest.
6. Checklist before departure
Before departure: open the airline's baggage page for each leg; measure the packed bag in centimetres and inches; weigh it on a scale; compare the total with the allowance; and buy extra weight online if you are over.