Colin FosterBy Colin Foster

Updated November 2026

For most day hikes, a backpack between 15 and 30 liters is the right size. For overnight trips, plan on 40 to 60 liters, and for multi-day treks of a week or more, 60 liters and up. Your torso length matters as much as capacity, so the best what size hiking backpack answer always accounts for both volume and fit.

Why Capacity Alone Doesn’t Settle It

Liter ratings describe how much space a pack holds, but they don’t tell you whether the pack will carry that load comfortably. A 50-liter pack with a torso that’s too long will sit on your hips awkwardly and shift every time you step over a log. A pack that’s too large also tempts you to fill every pocket, which adds weight you didn’t need to carry. Start with trip length to pick a volume range, then confirm the fit before you buy.

Shopping for one? See our guide: 4 Best Hiking Backpack Women's (2026): Expert Picks.

If you want a fuller walkthrough of fit, the guide on Hiking Backpack Size Chart: How to Find Your Torso Length and Pack Volume covers measuring your torso in detail.

The Factors That Set Your Ideal Size

Three things drive the decision: how long you’ll be out, how much gear your trip requires, and your body measurements.

  • Trip length: Day hikes usually need 15 to 30 liters for water, snacks, a layer and a first-aid kit. Overnights typically need 40 to 55 liters to hold a sleeping bag, tent and food.
  • Gear bulk: A bulky three-season sleeping bag can eat 15 liters on its own. Lightweight setups need far less room, so a smaller pack may work even for two nights.
  • Torso length: Most packs are sized by torso, measured from the C7 vertebra (the bump at the base of your neck) down to the top of your hip bones. Manufacturers specify size ranges for each model, and getting this right matters more than the liter count.

Owners often report that a pack fitting their torso well feels 10 to 15 liters larger than one that doesn’t, simply because the load rides where it should.

How to Choose Your Size Step by Step

  1. List your typical trip length and the gear you’d bring. Estimate total volume, then add 10 to 20 percent for food and water.
  2. Pick the liter range that matches your longest regular trip, not your occasional dream trip.
  3. Measure your torso length using a flexible tape or ask someone to help you locate the C7 bump and hip bone points.
  4. Match your torso measurement to the manufacturer’s size chart, not to the liter label.
  5. Load the pack with 15 to 25 pounds (or your typical load) at the store and walk around. Check that the hip belt sits on your hip bones and the shoulder straps don’t pull hard.
  6. Adjust the torso length and hip belt, then recheck the fit before buying.

What We’d Use

For a general-purpose daypack, the Osprey Talon 22 is a widely recognized option that many hikers choose for trips of a few hours. View on Amazon

For a single overnight trip, the Gregory Paragon 58 is a common choice with adjustable torso sizing that suits a range of body types. View on Amazon

FAQ

Is a 40-liter pack big enough for a weekend hike?

Yes, for most people carrying a lightweight shelter, sleeping bag and food for two nights, a 40-liter pack works well. Heavier gear or cold-weather trips may call for something closer to 50 to 55 liters.

Should I buy a backpack based on liters or torso size?

Torso size should come first. Liter capacity tells you how much fits, but torso length determines whether the pack carries the load comfortably.

Can a hiking backpack be too big?

Yes. An oversized pack encourages overpacking and can feel unstable when only partly full. If you mostly day hike, a pack of 30 liters or less is usually the better match.

Ready to choose one?

Colin Foster

About Colin Foster

Colin Foster is part of our editorial team and reviews and edits our backpacks & packing systems guides, checking product details against manufacturer specifications and owner feedback.