There's nothing worse than buying a 35 litre rucksack only to find that you can fit 25 litres of gear inside it!
So Trail Magazine measures the capacity of rucksacks using a recognised standard test method (Designation: F 2153 – 01).
In this test - used by a number of manufacturers including Lowe Alpine, Deuter and Osprey - plastic spheres are used to measure the rucksack volume.
Take a look at the video below where Graham Thompson, Trail’s Technical Editor, demonstrates the process.
Scroll down to see the video...