Choosing the right backpack size involves two critical measurements: capacity (volume) and torso fit. Getting both right ensures comfortable, efficient hiking on any trail.
For minimalist day hikes of 3-5 hours. Carries water, snacks, and a light shell. Best for fast-and-light trail running or short morning hikes.
Ideal for full-day hikes. Room for 2-3L water, food, extra layers, first aid, and safety gear. The most versatile size for day hiking.
For 1-2 night trips. Accommodates tent, sleeping bag, pad, cooking gear, and food. Choose larger sizes for winter or if sharing group gear.
For 3-5 night trips or winter camping. Provides room for additional food, clothing, and cold-weather gear.
For week-long trips or mountaineering. Necessary only for extended backcountry travel or expeditions with specialized equipment.
Tilt head forward. Feel for the prominent bone at base of neck (C7 vertebra). Measure from C7 down your spine to the top of your hip bones. This measurement, not your height, determines pack size.
Extra Small: 15-16 inches. Small: 16-17 inches. Medium: 17-19 inches. Large: 19-21 inches. Extra Large: 21+ inches. Many packs adjust within a size range.
A half-empty large pack carries poorly and encourages overpacking. Start smaller than you think you need.
A pack sized by capacity but wrong torso length will never fit properly, regardless of adjustments.
Always try on packs loaded with 15-20 lbs to assess true fit and comfort.
The right size backpack fits your torso properly and holds your gear without excess space. When in doubt between two sizes, choose the smaller option—you can always pack more efficiently but cannot make a pack fit better if it is too large for your frame.
Not recommended. Oversized packs for day hikes carry poorly, encourage overpacking, and wear you out unnecessarily. Use a 20-30L daypack instead.
Most hikers need two packs: a daypack (20-30L) for day hikes and a larger pack (50-65L) for overnight trips. One versatile pack rarely excels at both purposes.
Torso length, not total height, determines pack size. Two people of the same height can have different torso lengths requiring different pack sizes.
Check out our Top 100 Outdoor Gear guide with expert-tested recommendations.