By Marcus Hale, Lead Pack Research Editor · Published September 14, 2026, 6:03 PM ET
Direct Answer
There's no single "average" hiking backpack size, since the category spans daypacks to expedition packs, but the most common sizes hikers own fall between 20 and 50 liters. A typical day hiker's pack runs 18–22 liters, while a typical weekend backpacker's pack runs 40–50 liters.
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In plain English
Backpack size is measured in liters, which tells you how much stuff fits inside. A small daypack might be 15 to 20 liters. A big pack for a week in the mountains might be 65 or 70 liters, more than three times bigger.
Asking for the average size is a bit like asking for the average vehicle. A scooter and a moving truck are both vehicles, but averaging them tells you nothing useful. The same goes for backpacks: a pack for a morning walk and a pack for a week of camping do different jobs.
A better question is what trip you take most often. Short day trips need a small pack. Nights outdoors mean carrying a tent, a sleeping bag and food, which needs a much bigger one. Separately, packs come in body sizes, like shirts, based on the length of your back, so two people can need the same liters but different pack sizes.
Backpack size is described in liters of internal volume, and "average" depends heavily on what kind of trip the pack is bought for. A hiker who owns one all-purpose pack often lands in the 30–40 liter range as a compromise between day-hike and overnight use, but purpose-built packs cluster into fairly distinct bands by trip type.
Typical sizes by use
Use case
Typical size
Day hiking
18–22L
Big day hikes / fastpacking
25–35L
Weekend backpacking (1–2 nights)
35–45L
Multi-day trips (2–4 nights)
45–55L
Extended trips / winter loads
55–65L+
Why size varies so much
Trip length is the biggest driver, since each additional night adds food, fuel and often a bulkier sleep system. Climate matters almost as much — a winter multi-day trip needs significantly more volume than the same number of nights in summer, because insulated layers and a warmer sleep system take up much more space than lightweight three-season gear.
How liters relate to overall pack size
A pack's liter figure describes internal volume, not physical dimensions, so packs of the same capacity from different brands can look different sizes on the shelf depending on how tall, wide or deep they're built and how many external pockets add to the total. That's why fit — measured by torso length from the C7 vertebra to the iliac crest — matters as much as the liter number when choosing a size; a correctly sized 45L pack on one hiker's back can carry a load more comfortably than a poorly fitted 55L pack on another.
A practical way to think about "average"
Rather than chasing a single average figure, it's more useful to think in terms of the trip a pack needs to serve. A hiker building a first pack kit is usually better off buying for their most frequent trip type — day hikes for most people — and adding a second, larger pack later if multi-day trips become a regular habit, rather than buying one oversized pack meant to cover every scenario. An oversized pack for a short hike tends to ride poorly half-empty, while an undersized pack for a longer trip forces gear to be strapped on the outside.
Two sets of typical sizes, side by side
Typical ranges depend on who publishes them. This page's table runs 18 to 22 liters for day hiking, 35 to 45 for one or two nights, and 45 to 55 for two to four nights. The Washington Trails Association suggests 25 to 30 liters for a full-day hike, 45 to 50 liters for a standard one- or two-night trip, and 50 to 70 liters for three to seven nights.1 The gap between them mostly reflects gear assumptions: the smaller figures assume lighter, more compact kit.
Makers' own descriptions overlap the bands too. Kelty positions its 65-liter Asher for two to three days in the backcountry,2 while Osprey describes its Atmos AG 65 as built for heavyweight weekends or week-long trips.3 Pack families come in steps rather than one size: TETON's Scout line is sold in 45, 55 and 65 liters,4 and Hyperlite's Southwest in 40, 55 and 70 liters.5 There is no single middle size, only common steps.
Why the liter figure is not the whole story
Stated volume often includes exterior pockets. Gossamer Gear's Mariposa 60 holds 60 liters in total, but only 36 liters are in the main body, with 24 liters across seven exterior pockets.6 A pack with a big front mesh pocket can post a high number while carrying bulky items less neatly.
Volume also says nothing about how much weight a pack is built to carry. REI says its Flash 55 is comfortable with loads up to 35 pounds,7 and rates its Traverse 60 frame for loads up to 45 pounds.8 ULA's Circuit holds 68 liters but lists a 35-pound maximum load.9 Two packs of similar size can be designed for very different loads.
Gear weight shifts the answer
The biggest reason one hiker needs 40 liters and another needs 60 for the same trip is the gear itself. The Appalachian Trail Conservancy calls the pack, shelter and sleeping bag the big three, usually the heaviest pieces of gear,10 and they tend to be the bulkiest too. Gossamer Gear defines lightweight backpacking as a base weight under 20 pounds and ultralight as under 10 pounds.11 Lighter kit usually packs smaller, which is why ultralight hikers carry smaller packs than the 'average' tables suggest.
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