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How to Size a Backpack: Daypack and Backpack Volume Guide

How to Fit a Backpack - Daypack and Backpack Volume Guide

Recommended Backpack Volumes

How much volume should you get in a daypack, weekend backpack, multi-day backpack, or expedition backpack? Here are some volume guidelines and advice so you can start shopping for backpacks in the appropriate size range.


Most daypacks range from 20 liters to 35 liters on the high-end. While a smaller sized backpack is usually sufficient for 1/2 day hikes, you’ll want a larger pack in the 35-liter range for all-day hikes so you can carry extra water, food, clothing, and the 10 essentials. The daypack category also includes hydration packs which can be a good option. Just make sure that you have sufficient volume to carry your extra gear.

If you’re a winter day hiker and snowshoer, I’d recommend sizing up to a 40-45 liter backpack capable of carrying snowshoes, microspikes, and bulkier insulated clothing. You need a beefier backpack than a small daypack to carry snowshoes when they’re not needed.

Weekend Backpacks (1-3 Nights)

You can’t use most daypacks for overnight and weekend backpacking trips because you need to carry a lot more gear, such as a sleeping bag/quilt, sleeping pad, sleeping clothes, tent/shelter/hammock, stove, cooking pot and utensils, and more food.

All this extra stuff requires more space, even if you take a minimalist or ultralight approach to gearing up. For a 1-3 night weekend trip, the sweet spot is going to be a backpack with 40 to 50 liters of volume.

Multi-day Backpacks (3-5 Nights)

The biggest difference between shorter weekend and multi-day backpacking trips is the need to carry more food and possibly a bit more technical gear, depending on the kind of activities or climate you’ll be hiking in.

For multi-day trips, you’re going to want 50 to 70 liters of backpack volume, but if you go ultralight or use compressible gear that doesn’t take up a lot of space, you might be able to get by with less than that.

Expedition Backpacks (5+ Nights)

Expedition backpacks are the behemoths of the backpacking world and range in size from 80 liters up to 110 liters or more. They’re designed to hold a mammoth amount of food and gear, usually for professionally guided mountaineering trips. If you’re going on a trip like this, it’s probably worth asking your guide for backpack recommendations. They may also have gear that you can rent since expedition backpacks can be quite expensive.

How Backpack Volume is Measured

Most major backpack manufacturers measure the volume of their backpacks by adding up the total volume of the closed storage on their packs, including the main compartment, pockets, and hip belt pockets that can be closed or zippered shut. However, many smaller manufacturers use a different method and include open pockets like side water bottle pockets or rear mesh pockets in addition to the closed storage. This can make weight-to-volume comparisons a little misleading when comparing packs from different manufacturers When in doubt, contact the manufacturer to ask what method they use to measure backpack volume.

You can use a smaller backpack, with less internal storage, if you can attach gear to the outside of it
You can use a smaller backpack, with less internal storage, if you can attach gear to the outside of it

External Attachments

If you plan to carry a lot of bulky gear, you don’t have to carry all of it inside the closed storage of a backpack. Bulky sleeping pads, tents, rain gear, snowshoes, and water bottles are commonly stuffed into exterior pockets or attached to the sides, back or bottom of a backpack with webbing or compression straps. This lets you use the same backpack for medium and longer trips, without having to buy a second larger pack to carry your extra gear.

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Updated 2019.

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  1. There seems to be a big gap on the low end. It goes from 1/2 day (food, raingear, extra layer) to 1-3 days. How about something for a dayhike (lunch in the woods) to overnight?I am thinking for an overnight I can get everything into a 30L, and that could be shrunk for use on a dayhike. Right?

    • It kind of depends on what, when, and where you plan to do your overnight (depends on weather, remoteness, hostile wildlife, insects). For assuming a temperate 3 season setting, if you brought a 1 person tent and a 40 degree sleeping bag, a stove, food, bear bag, water filter, and sleeping baselayers (which I highly recommend) that will add about 15-25 liters of gear to your backpack. If you can shrink your entire contents to 30 go for it. Personally, I usually fill about 35 liters of a 40L pack for every 1 night trip I take. But the night 2 and 3 loads only consist of extra food. That’s why there’s such a big jump on night 1.

  2. Pretty cool read. Good info.

  3. I still have no idea what a 35L looks like

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