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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’s a lot of …. salesmenship involved in sizing backpacks. The main volume can be one size in the design and anotherin the final product. “Limpet” stle exterior pocket are more honest than patch pocket but an “n” liter exterior pocket, mesh or not, may not maintain its full volume when the main bag is full and the contents are bulging out.

  2. I find the straps and attachments on the outside of the bag to be just as important as the volume. For example, my wife’s Osprey 33 has a weird assortment of hoops and straps that are very asymmetrical and difficult to attach long items, such as sleeping pads, umbrellas or tents. She’s learned to live with and the bag has served her well, but it is frustrating.
    On the other hand, my rather inexpensive (all things considered) Kelty Redstone 70 is marvelous for attaching things. I needed to purchase this pack at the last minute before going off on my hike of the Vermont Long Trail last summer and was pleasantly surprised with its utility.
    What I really need is a 110 litre belly bag to carry all of my food and treats as I hike along.

  3. Where do you store your ham radio?

  4. Excellent concise guide, thank you. I want to take my wknd pack (80L) and by pairing it with a Ribz frontpack, extend it to a 100L extended/multiday system. We’ll see how it goes…

  5. Just remember that a liter is 3 ramen noodle packs, so if you convert all the volumes to ramens, you’ll be able to visualize them well…

  6. Thank you for this piece of writing. I’m currently looking to replace a very old and somewhat heavy multi-day backpack and you’ve conveyed some very useful information.

  7. I find 65 to 75 litres to be just right for your typical 2 to 3 nights, allowing just enough room for more longer trips if needed. Currently have a REI Crestrail 70 and Gregory Baltero 75 and love them both…

  8. I’ve never gone over about 45 liters even carrying ten days’ food.

    The cubic inches-liters table isn’t really necessary. For quick and dirty calculations (especially since pack volumes aren’t all that accurate anyway), there are approximately 60 cubic inches in a liter. I suspect that most or all of us can multiply or divide by 6!

    • Really. I certainly have…and I always use google to translate cubic inches to liters!

    • Interesting because most of my gear is ultralight or lightweight at worst. marybe I carry a couple extras for my 9 year old daughter and or wife but on a 2 or 3-night trip im using most of those 65 to 75 liters..More power to you but don’t see how one can fit everything at ease in a 45 liter pack. I don’t mind the bigger pack and carrying capacity at the expense of a couple extra pounds just amazed you can fit everything!!

  9. Living in most countries outside North America the conversion to cu ins isn’t necessary

  10. Both “main” packs I’ve owned have been in the neighborhood of 4000 in3, and I’ve felt both were a little small, though I suspect that feeling came from minor design gripes and having less compressible gear more than actually *needing* more space.

  11. I have to remind myself that it’s always easier to carry less than your backpack can hold than more. Sounds overly simple but I got caught up in trying to get too granular with my pack sizing. Of course, there is the risk of taking more than you need (guilty), but I’d rather that than be unprepared.

  12. I’m trying to roughly size up my old Outgear pack. Ive had it since I was in High School back in the 90’s, I could fit sleeping bag, tent, cooking gear and food, sleeping mat and clothing in it, enough for 3 days generally.

  13. If you ever do the boundary waters or anything wet, I highly recommend the waterproof SealLine backpacks. 30L was enough room for all my gear (12 lb gear, 6 lb food) + I had to portage a canoe that can weigh up to 80 lb. For longer than 4 day treks I would add an extra food pack into the mix and a bit more gear + a book. But, never beyond the 30L pack and a smaller daypack. Could easily manage 8 days on the water. (I’ve done this type trip a dozen+ times, and countless hiking trips of 50+ miles with the same gear)

    Pro tip: Use a sleeping pad as the shell of the pack, and pack everything inside that.

  14. Wow I am trying to buy a new daypack and found your sizing to be off. I have used a 60L pack as my multiday one for the last 25 years. I have a 100L backpack that didn’t get used until I had young kids and had to carry everything for 3 people (my 2 kids and me my wife carries her own gear). I would suggest 35L with the right gear could be 3 days but a lot depends on your gear and comfort level. If you need new clothes every day and a synthentic sleeping bag then go bigger. If you dehydrate all your food and use a down sleeping bag go smaller. Just my two cents other than the sizes being a bit on the large size a good article

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