Generally, a 30L backpack has a length of around 19-21? (or 48-53 cm) and width of 10-12? (25-30 cm). They generally weigh between 2.5 and 4 pounds. These backpacks are quite spacious too they generally have a depth of 10-12? (27-30 cm). So, you can quickly go on a trip of a few days with it.