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.

Daypacks

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.

See Also:

Updated 2019.

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15 comments

  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

    • They all look different depending on the backpack make and model. But if it helps, it’s slightly larger than a paper shopping bag in terms of volume.

    • 35 liters is roughly about 2500cubic inches which is roughly about 1.5 cubic feet or about 9 US gallons using very approximate conversions.

      Grocery bags actually vary quite a lot it seems but the ones I have and think are typical are about 1200 cui which is about 20 liters or 5 US gallons.

      I was actually surprised how much gear I can get in my REI Traverse 35 which is nominally a 37 liter pack. I measured it and that is the size of the main compartment with the draw string loose.

      Here is the list…

      Main Bag…from bottom to top

      Kelty Light year 20 sleeping bag in compression sack
      Thermarest Xlite regular
      Inflatable pillow
      OR Transcendent hooded puffy
      Sleepwear and Spare clothing Stuffsack…Merino Half zip, long underwear, briefs, wool boot socks
      BA TigerWall UL2 Tent (poles, stakes and footprint in separate bags…poles are vertical down one corner)
      Warm clothing Stuffsack…beanie and insulated gloves
      Soto Amicus cookset stove combo

      Back Zip Pocket…

      Rain Jacket and Pants
      Trowel+Bidet etc.

      Brain…

      Sawyer Squeeze Filter and CNOC Vectro
      First Aid Kit
      Repair Kit
      Headlamp
      Buff
      etc.

      Hip belt pockets…

      Bug net
      Trekking pole tips
      Lip grease
      Small tube of sunscreen

      Outside

      Xero sandals (for camp/river crossings) These could go in the back “mesh” pouch but I strapped them in the “lifter”)

      That lot weighs 18.2# with the pack and is a fairly impressive list for a “day pack”. While some of that gear is quite light weight and low volume, some of it isn’t. I didn’t use either the back or side mesh pockets and there was a bit of room left inside for food for a day or so.

      The pack was obviously a bit overstuffed so may not be that comfortable to carry like that for very long. The top end of the mesh back was touching the bag. I would definitely trim the list for actual 1-3 night use…and probably only consider using it for summer when bad weather is unlikely.

      • I suspect that REI does not include open pockets in their volume calculation. Most major brands don’t. There’s actually an industry standard for this, which small manufacturers ignore or don’t know about. In addition, if you have the large size, the volume is actually 37 liters.

      • I think you are right about that based on my measurement although synch’ed up the main bag measures out at more like 32L. REI also gives a rather odd dimensional size of 27 x 12 x 11 which is ~3500cui or ~57L and it is unclear what that is supposed to indicate… REI don’t actually list the Traverse 35 as a day pack although various reviewers do and I bought it with that in mind. I did think it might be a bit overkill for that purpose but having suffered from floppy light weight day sacks that tire you out carrying a liter of water and a jacket if you go more than about an hour with them, I thought it was worth a try.

      • I regularly carry a 38L pack for day hikes in the mountains. Of course, it snows year-round here and I often bring a few pounds of fly fishing gear with me.

  4. Ok, so we are planning a week hiking but will be staying in B&B, pubs and hostels overnight. All that I’ve read accommodates camping equipment and food which we’ll not be taking (other than snacks and possibly mid-day picnics). How would that affect the pack sizes you are recommending?

  5. .I use a 38 liter for everything from overnighters to 30 day trips, and a 9 liter 28g pack for day hikes.

    • Yes, but most of the people who are searching for an answer to this question are probably not ultralight backpackers or trust fund babies. You can eventually reduce the volume and weight of your gear if you really put your mind to it and you’re willing to pay the big bucks (or just hike in nice weather). The rest of us like to carry a few extra bulky comforts and don’t do 30 day trips!

    • Also there is no way you are carrying 30 days of food in a 38 liter pack so probably you are really doing 10 3 day trips back to back.

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