Travel backpacks: how does capacity compare with weight?

No. These are the makers' travel packs for clothes and travel gear, and trail features such as hip-belt load carrying aren't compared here. For day hikes, a daypack comparison is the better starting point.

Each capacity is the maker's standard figure, without expansion; Tortuga's Expandable Backpack, for example, is rated at 27 liters, and its expanded size is on Tortuga's page rather than in this table. Among the five 35–40 L packs, Eagle Creek Tour Lite 38L weighs 1,100 g and Aer Travel Pack 4 35L weighs 1,769 g.

Eagle Creek's title says 28L while its spec table matches Tortuga’s standard capacity above, and the depth disagrees too, so both stay blank. That means any capacity minimum hides it, even though at 900 g it's the lightest of the nine packs with a stated weight. The 55 L Tour Travel Pack runs 25 in on its first dimension, against 19 to 23 in for every other pack, so hold it to your airline's cabin limit.

This comparison can't say. Makers' outer sizes help you rule packs in or out against an airline's published limit, but torso fit, loaded comfort and whether a gate agent accepts the bag aren't covered.