How to Choose a Backpacking Backpack | Fit, Volume & Features That Matter

The wrong pack turns a great trail into a miserable one. Too big and you carry dead weight. Too small and you’re strapping gear to the outside. Bad fit and your shoulders take a beating. The fix is a systematic approach: know your trip length, measure your torso, then match features to your gear. Here’s exactly how to do it.

What Size Backpack Do You Need By Trip Length?

Pack volume is measured in liters, and the right range depends entirely on how many nights you’ll be out. Day hikes need 15–25L for a rain shell, food, and water. Overnight and weekend trips (1–3 nights) work well with 40–55L. Multi-day week-long trips call for 60–70L. Winter and expedition trips require 65–90L to accommodate heavier insulation and sleep systems. The general rule: pack everything you plan to carry, weigh it, and pick a volume with only about 10% spare room—not 30%. That extra empty space adds weight and bulk you don’t need.

New backpackers typically carry a total pack weight of 20–30 pounds. If your gear (excluding the pack itself, food, and water) exceeds 10 pounds, you need a pack with an internal frame and a thick padded hip belt to handle it.

How To Measure Your Torso For The Perfect Fit

Backpacks fit by torso length, not height—yet buying by height is the most common mistake people make. Most adults have a torso length between 16 and 21 inches. To measure yours, have a friend find the C7 vertebra (the big bony lump at the base of your neck) and measure straight down to the top of your hip bones (the iliac crest). That number is your torso length.

Try on the pack with 8–12 kg of weight inside (books or water bottles work). An empty pack masks suspension issues and tells you nothing. When adjusting the straps, cinch the hip belt first—it must sit on top of your hip bones, not above or below. Tighten shoulder straps and then the load-lifter straps. When the fit is right, roughly 70% of the load should rest on your hips, not your shoulders.

Frame Types, Materials, And Key Features

For backpacking where you carry everything on your back, an internal frame pack is the standard recommendation. It keeps the load close to your body for better stability on uneven terrain. External frames were common decades ago but are generally preferred for hauling heavy, bulky loads short distances rather than for multi-day backpacking.

Fabric durability is measured in denier. Look for 400 denier or higher to resist tears and abrasion over years of use. A 50–60L pack that weighs around 4 pounds generally offers the best balance of capacity, weight, and durability. Our tested roundup of the best backpack for mountain biking covers similar fit priorities if your gear crosses over between sports.

Key features to evaluate include: pockets and organization for quick-access items, a sleeping bag compartment if you carry one, a rain cover or integrated rain flap, and a removable day pack for summit pushes or side hikes. Manufacturer weight ratings include a “comfort range”—staying within that range keeps the pack feeling stable on your back. Every brand fits differently, so always test the specific model in a store with weight loaded.

Common Mistakes When Choosing A Backpack

The biggest errors are predictable and avoidable. Buying by height instead of torso length leads to poor load transfer and shoulder pain. Buying a pack 30% larger than needed adds unnecessary weight that you carry for miles. Trying on a pack empty tells you nothing about how the suspension behaves under load. And buying a pack before reducing your gear inventory almost guarantees an oversized bag—the smarter order is to reduce gear first, then buy a pack slightly smaller than the gear allows.

If you have chronic pain issues, prioritize a lighter overall load to reduce injury risk. Body-weight percentages are rough guidelines, not rules. The real test is how the pack feels on your body for a few loaded minutes inside the store.

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