Litres, centimetres and grams on a bag

Litres: capacity, and only capacity

Volume tells you how much fits. It says nothing about shape, and shape is what decides whether a 16-inch laptop goes in a 26-litre bag. Two bags of the same volume can take completely different things.

Use litres to compare bags of the same type against each other, never across types.

Centimetres: the number airlines read

Outside dimensions decide whether a bag boards. They are also where measurements diverge most between brands: some measure the body, some measure with handles and full front pockets.

We publish the outside dimensions of the empty bag, which is the conservative number and the one a sizer applies.

Grams: what you carry before you pack

A leather weekender weighs 1.8 to 2.4 kg empty. On an airline with a 10 kg cabin limit that is a quarter of the allowance spent on the bag.

It is the number most sites omit. Ours is on every page, because there is no way to work it out from a photograph.

Reading them in order

Start with centimetres if the trip involves a plane, because a bag that cannot board is not a candidate whatever it holds. Then litres, to check it takes the days you are away. Then grams, to check what is left of the allowance.