Pack Size by Trip Length

Capacity is measured in litres, and the number is less intuitive than it looks. Here is roughly how litres map to trips.

Under 20 litres

A day out. Enough for a jacket, a water bottle, lunch and a small camera, or a laptop and a notebook for a commute. Too small for a change of clothes and toiletries together.

20 to 30 litres

An overnight trip, or a very disciplined weekend. This is also the sweet spot for commuting, because it swallows a laptop, gym kit and a coat without becoming unwieldy on a train.

30 to 40 litres

The carry-on range, and where most travel packs live. With packing cubes and a willingness to do laundry, this is genuinely enough for two weeks. Above about 40 litres you are usually past cabin limits.

40 to 50 litres

A week or more without laundry, or travel in cold weather, where insulation eats volume quickly. Usually checked rather than carried on.

50 litres and up

Multi-day hiking with your own shelter and food, or family travel where one adult carries for two people. At this size the harness matters more than the volume.

Why bigger is not safer

A bag gets filled to its size. The most common packing mistake is buying one size up "just in case" and then carrying five kilos you did not need. If you are between sizes, take the smaller one and a packable daypack for the overflow.

Cold weather shifts everything

Winter clothing is bulky rather than heavy. A trip that fits 30 litres in July can easily need 40 in January, which is why the season matters as much as the number of nights.