What size backpacking pack do I need for multi-day trips?

Across mainstream reviewers and specialist subreddits, 55-65L is the most commonly recommended range for 2-5 night trips with conventional (non-ultralight) gear. 50L can work if your kit is light and compact; 70L+ is generally flagged as overkill that encourages overpacking, with multiple community threads warning that 80-100L bags only carry well when loaded heavily.