20 L Backpacks

A rucksack 20 litres is the perfect everyday size: it can fit a laptop, a pencil case, a water bottle, and a lightweight jacket without overflowing. It's the right size for commuting, school days, and trips into town. Beyond that, you move to 30 litres, suitable for an overnight stay away from home.

What's really inside a rucksack 20 litres

At this size, the useful measure is not the volume displayed but the width of the main compartment. An A4 folder lays flat, a laptop slips into the back sleeve if available, and there's space for a light sports outfit. Slim straps and shorter backs are available in rucksack 20 litres just like in others, they change how you carry it, not the capacity.

Choosing a rucksack 20 L for the city

Three details set apart two similar models. The padded back, which prevents a charger from leaving an imprint between the shoulder blades. The closure, whether it's a two-way zip or a flap, depending on whether you open the rucksack ten times a day or two. And the fabric, a coated polyester that holds up better in the rain than cotton canvas. A rucksack 20 L for city use is also judged by its front pocket, the only one you can access while standing on public transport. Urban brands like Eastpak, adidas, and Kipling dominate this capacity, while Dakine and Nike offer more technical models.

Measuring a rucksack before taking it on board

A volume doesn't say much about the size, two bags of the same capacity can take up very different spaces. The method involves three simple steps.

• Pack the rucksack as it will be on departure day, including the front pocket.
• Place it against a wall and measure its three dimensions, including straps and external pockets.
• Compare these measurements against the dimensions published by the airline, price by price.

We do not take any permitted dimensions here, they vary by carrier and according to the ticket purchased. The size of a rucksack 20 litres already varies by several centimetres from one brand to another, so it’s the rucksack that needs measuring, not the advertised capacity.

The search “ rucksack 40 x 30 x 20 cm” comes up often: it’s the size under the seat for several low-cost airlines, to be confirmed on the carrier's website before buying.