What size hip pack do I need for day hiking?

Across the reviewers we read, 1–3L is the sweet spot for short day hikes carrying snacks, phone, keys, and a small layer, while 5L+ packs with hydration bladders or twin bottle pockets are favored for longer hikes, mountain biking, and trail running. Specialist communities consistently note that bigger isn't better: oversized packs bounce and dig into the lower back when underpacked.