Confusion on size of pack needed

I will be doing my first overnight trips this year. I already have a 1-man tent, sleeping bag, pad, stove, etc. I have a few smaller items to procure yet, but we're getting there. I am not demanding the lightest gear out there, but I don't want heavy (i.e. milsurp!)

Question is, how big of a pack do I need for such a trip? I read that 4000" is the minimum. Others suggest something bigger in the event I do some cold weather trips. If this helps, I'm an Osprey fan when it comes to packs, but am not afraid to try other makes as well.

I welcome any and all comments. Thanks.

What matters is fit, fit , and fit. How the pack fits you, how the pack fits your gear, and how the pack fits you with your gear.

It is you and your gear that matter. Many people recommend boxing up your stuff and going to the store during non-busy hours and put your stuff in the pack.

I will say, in general, a 4000 in3 pack is on the large size for lightweight backpacking. However, if you have a big synthetic sleeping bag, it would take up most of that volume.

In my opinion, the downside to having extra space, is humans tend to fill it. That is one significant way you get weight creep. I would not recommend getting a pack to fit gear you might get in the future.

BZH has "stolen" my lines, so I'll just say that I fully agree with him! In addition to taking your gear, be sure to take the weight/bulk equivalent of a week's food and a day's water for the pack tryon.

Take a look at articles on the home page of this site, left hand column for more info on selecting a pack and other gear.

Thanks for the replies. I never really looked at it that way... So are you suggesting I should get a smaller pack (say 3300") and choose my gear to fit?

I have to mail order everything. We have nothing within reasonable driving distance that sells *real* gear. Hence the reason I am looking for a starting point here...

Put all your gear in a bag, see if you can make it somewhat rectangular and measure the width, height, and length. Say you get 15"x 30"x12" . Your total cubic inches = 5400. You need a larger size pack or something in the 90 liter range. Now that's a big expedition pack, but you get the idea. That size can be reduced by strapping things outside the pack, like a pad or your tent. Not all packs will carry the same, nor pack the same. Some are narrow and will not hold a bulky sleeping bag, or have an opening that is too small too fit one in. Some have more capacity in outer pockets than the main compartment. Some have the capacity primarily in one big bag. Some have a sleeping bag compartment, but most will only take smaller, compressible bags, not big synthetics. Decide what you need depending on what you'll bring. If you want to spend more money to downsize, you can, but if you can't, figure up what you have. If you're an Osprey fan, their website has a good explanation how to fit and size a pack. I recently bought an Atmos 50 and love it. I dialed in the fit exactly the way I want it (lots of adjustments!) and a couple hundred miles of winter trails later it hasn't changed. In recent years I've used much lighter packs and paid the price every time I had to add weighty items like lots of water or things out of my wife's pack because she wasn't feeling well. The fact that the pack is heavy itself is well belied by how well it carries. If you buy from REI or another reputable supplier with a good return policy, you can make sure you get what you need. Make sure your gear is clean, or put it in plastic bags and see if what you thought worked, does. There's a company down towards Harrisburg called Backcountry Edge that could be helpful. I had some conversations with them on the phone and they were very cool. They are also avid backpackers and could even help with places to go in Pa. I would call and have a conversation with them when I thought I had a handle on what I wanted. They're an Osprey dealer, too. https://www.backcountryedge.com/manufacturers.html

Thanks for all the great replies so far. I guess it comes down to whether I want to move fast and do without, or move slower and have a few perks. I have a feeling I will lean towards a bigger pack as some of my children may come along on some trips as well. Although I have small packs for them, it may be more of a novelty than anything.

Well... I really don't like to recommend a size.... but having a bag that just fits your gear is a good way to prevent you from bringing stuff you don't need. What size "just fits your gear" is a hard number to estimate. When I started, I had ~4000 in3 pack and couldn't fit everything in it that I wanted to. I have come to realize I didn't need the stuff I couldn't fit. With experience and a couple purchases I can go out two nights with all the gear for me and my son in that same pack. My stuff would nicely fit in an ~3300 in3 pack now.

p.s. Sorry Mouse for stealing your spiel. I didn't know how quickly you would jump in your retirement

Just got thinking about this... I could invest in a larger 4000'ish pack now, do a few trips to see how it goes. If I find myself taking too much, downsize to a smaller pack for the rest of the season and save the larger pack for winter camping.

One can never have too many packs, eh?!

Unless you can afford a lot of packs, probably not. Besides, a pack that's too big for your stuff will not carry correctly.

Don't even think about ordering a pack until you have all your gear, (plus, as I said, the equivalent in weight and volume of a week's food and a day's water). Weigh it all, then pack it in a box and measure the volume (length x width x height). This will give you an approximate measure (do note that pack volume is a very approximate number anyway). Since most pack sizes are now in liters, note that 1 liter is approximately 60 cubic inches. When researching packs, be sure to check pack specifications on the manufacturers' websites--subtract 5 lbs. from the recommended maximum weight since for most people that number is overstated.

Leave your stuff in the box. As soon as the pack arrives, pack your stuff in it and carry the load around the house for a couple of hours. Be sure to leave the tags on the pack and keep it clean, so you can return it if it doesn't work.

I was lucky when I ordered my pack--the first one I ordered fit as though it had been custom made for me. I was fully prepared to pay return shipping on half a dozen packs to get one that worked for me.

A common way for manufacturers to determine their pack size is to use polystyrene balls/beans to fill the pack then transfer those into a box and measure.
From that the volume is rounded off to the nearest common size.
(not always as there are 548L and so on packs...)
Most manufacturers add the real or imagined external pockets volume, I say imagined because often you can't fill those pockets if the main compartment is full already.
(check photos of the full pack in Google Images )
Do make sure that you have water/food and fuel included in the volume required.

And volume's not the only issue. Once, I knew "someone" who selected a pack because it was big enough to hold his load, but not too big. He forgot to check out the suspension. The first time he took it out, he soon found out that the 30 pound load in the nifty little 2.5 pound pack had caused the hipbelt to double over, and rendered the lightly padded shoulder straps virtually worthless. Doing further research, he discovered the maximum comfort rating for the pack was 20 pounds.

Be sure you not only get the right size for the volume of your gear, and also a suspension beefy enough to carry the weight of your gear comfortably. (30 pounds of ultralight gear weighs the same as 30 pounds of traditional gear, oddly enough.)

Yes.
An extra pound in a well built pack could make your load feel 5 or 10
pounds lighter.
A plastic shopping bag can carry 8 or more pounds , yet you don't see many hikers carrying their load in three or four shopping bags.

Ultra-dirt-bagging for the win!

Dirtbagging? I grew up kinda poor , so when I decided to go camping for the first time, I put a bunch of stuff in a torn laundry bag, threw it over my shoulder and headed off to a large tract of woods. My parents wouldn't pay the dues or buy uniforms for me to be a boy scout, so I made do. The next day, I got stopped by the police as I walked home on the side of a highway. They were sure I was a runaway, or a thief. I didn't know it until I got home, but I had gotten soot on my face from my campfire and looked as if I was engaging in some type of stealth activity. It took me awhile to convince the cops that I was innocent of wrongdoing. I had been trespassing, but I sorta prevaricated around that part. I did advance to an old Army pack that was given to me by a neighbor, but it wasn't much better than the laundry bag. My first external frame was a game changer. I have a number of friends that were in the military that would rather be water- boarded than backpack. A pleasant first experience might be a good thing. I was too young and stupid to have anything imprint. When I was in college, I was the co-advisor for a high school backpacking club in a wealthy community. Those kids had the latest and greatest. I envied them, but I imagine many of them still are on the trails. Nature has a gentler, more beautiful aspect when a pack isn't creating fiery ruts in your shoulders and hips.

I spoke with a fellow co-worker today that did the AT a few years ago. He told me the same thing.