Choosing a hiking backpack starts with torso length, not height, then matches capacity to trip length.
For the full breakdown, see our best Day Hiking Backpack with Hydration guide.
A pack that doesn’t fit your body or match your trip turns a pleasant trail into a misery of sore shoulders and an aching lower back. The fix is methodical and takes about fifteen minutes with a tape measure. Start with your torso length, then match the capacity to your trip, and you’ll narrow the field before you even look at features.
Measure Your Torso First: Fit Beats Height
Your height tells you almost nothing about which pack fits. REI’s guidance is blunt: torso length—not height—is the key sizing metric for a backpack. Two people of identical height routinely need different pack sizes because torso length varies independently.
Here’s how to get your number:
- Find the C7 vertebra. Tilt your head forward and feel for the most prominent bone at the base of your neck—that’s C7.
- Locate the iliac crest. Place your hands on your hips; the top edge of your hip bones is the iliac crest.
- Measure between them. Have someone run a tape measure from C7 down your spine to the iliac crest. That distance, in inches, is your torso length.
Compare that number to the manufacturer’s sizing chart. Charts vary between brands, so always check the specific pack’s chart rather than assuming one size translates.
Match Capacity to Your Trip, Not a Magic Number
Pack capacity is measured in liters, and the right range depends on how many nights you’ll be out and how much bulk your gear occupies.
| Trip Length | Capacity (Liters) | What Fits |
|---|---|---|
| Day hike | 15–25 L | Layers, food, water, small first-aid kit |
| 1–2 nights | 20–50 L | Light overnight gear, sleeping bag strapped on |
| 2–3 nights | 50–60 L | Tent, sleeping bag, pad, stove, food |
| 2–5 nights | 60–80 L | Full camping kit plus extra food and layers |
| 5+ nights | 80+ L | Expedition gear, bear canister, winter layers |
A weekend hut-to-hut trip with no tent or stove might fit in a 25–32 liter pack, while a week-long expedition demands the large end. The single most common mistake is buying one “all-purpose” pack that’s too big for day hikes and too small for real trips. Decide what you’ll actually do most, then size for that.
Check the Carry System: Hips Carry the Load
If the weight sits on your shoulders, the pack doesn’t fit.
- Hip belt sits on your hip bones, not your waist; it should wrap fully around and feel snug when buckled.
- Shoulder straps curve over your shoulders and connect to the pack about 1–2 inches below the top of your shoulder.
- Sternum strap buckles at chest level and keeps the shoulder straps from sliding outward.
Walk around the store with the loaded pack. Jump, bend, and twist. If the pack shifts or the hip belt rides up, it’s the wrong size or shape for you.
Once you’ve dialed in torso length and capacity, the final decision comes down to features and price.
FAQs
How do I measure my torso length for a backpack?
Tilt your head forward to find the C7 vertebra at the base of your neck, then measure straight down your spine to the top of your hip bones (the iliac crest). That distance in inches is your torso length. Compare it to the manufacturer’s size chart, since ranges vary slightly between brands.
Is a 50-liter backpack too big for a day hike?
For most day hikes, a 50-liter pack is unnecessarily large. A 15–25 liter pack handles typical day-hike gear like layers, food, water, and a first-aid kit. A 50-liter pack is better suited to overnight or weekend trips where you’re carrying a sleeping bag, pad, and tent.
Should a hiking backpack sit on my hips or shoulders?
References & Sources
- REI. “How to Choose a Backpack.” Official sizing guidance on torso measurement and capacity ranges by trip length.
- Washington Trails Association. “How to Choose a Backpack.” Trail-savvy advice on matching pack size to trip type and measuring torso length.