Backpack size guide
Too small and your jacket ends up strapped to the outside. Too big and you carry air and pack too much. The guide asks about trip length, where you sleep and the season, then gives you a range in litres to shop by.
Loading the app …
How the calculation works
The sum is a rule of thumb built from blocks: 18 litres for basic kit and 3 litres per day for food and spare clothes, counted up to seven days. Camping adds 18 litres for tent, sleeping bag, mat and stove; winter adds 8 litres for bulkier clothing.
The result is rounded to the nearest 5 litres and shown as a range with about 8 litres of headroom.
How to read the result
Shop within the range. The lower end suits compact packers, the upper end suits you if you need room for supplies or shared group kit.
From about 40 litres, an adjustable back system matters more than a few extra litres.
Frequently asked questions
Why does the sum stop at seven days?
On longer trips you usually restock along the way or eat in huts, so the volume hardly grows.
How do I find my back length?
Measure from the bony bump at the base of your neck down to the top of your hip bones. Many packs come in several back lengths or with an adjustable harness.
Do I need a rain cover?
Most backpacks are not waterproof. A cover or dry bags inside keep your sleeping bag and clothes dry.