The Carry-On Guide

Most airlines allow one cabin bag and one personal item. The limits vary more than people expect, and the way they are enforced varies even more.

The dimension that actually matters

Cabin size limits are usually quoted as three numbers, and the one that gets bags rejected is depth. Length and width are checked casually, but a bag that is too deep will not go into a sizer frame at all, and a soft bag packed round is deeper than the same bag packed flat.

A common domestic limit is around 56 x 36 x 23 cm. Many European carriers are smaller, and low-cost carriers smaller again. Check before you fly rather than after.

Weight limits are the real constraint

Plenty of travellers get caught by weight rather than size. Limits between 7 kg and 10 kg are common in Australia, Asia and Europe, and 7 kg is not much once a laptop and a pair of shoes are in the bag.

This is why the empty weight of a bag matters. A pack that weighs two kilos has spent nearly a third of a 7 kg allowance before anything goes in it. A wheeled bag costs even more, because the wheels and handle are heavy.

Structured or soft

A structured bag holds its shape and is easier to pack, but it cannot be squeezed into a sizer. A soft bag can be compressed at the gate, which occasionally is the difference between boarding with it and checking it.

The personal item

The second bag is the one people waste. A small sling or packable daypack that holds a tablet, documents and a water bottle lets you take the bulk out of the main bag at the gate, and gives you something to carry on the day itself without taking the big pack.

Rules of thumb

• Measure your bag packed, not empty.
• Weigh it at home. Airport scales are not on your side.
• Keep anything you cannot replace in the personal item.
• Spare lithium batteries must travel in the cabin, never in checked luggage.