Price per piound

[Paul Wagner]

Had some fun with this yesterday: it's from our blog on backpackthesierra.com

Is there a mathematical solution to the challenge of ultralight backpacking? It seems that an engineer would be able to develop an equation that could be used to fine tune our equipment. It would have to address a number of variables. I am not an engineer, nor do I play one on TV, but I did have some fun working through this problem:

W = the weight of your pack when you leave the trailhead. The goal is to manipulate the other variables to achieve a very low value for W. Lighter is better

P = the price you have to pay for your equipment, in dollars. Please convert from Euros, Rubles, etc. if required.

And somehow our equation needs to reflect that as W is reduced, P usually increases.

In fact, as W approaches zero, P probably arrives close to infinity—or at least beyond the reach of normal people. In other words: Priceless. Ouch.

Instead, let’s set up the equation to reward people who do this lightly and CHEAP.

So with all that in mind:

LET

W = Weight in number of pounds you carry. Note that this will NOT be what you WANT to carry which will always be N-1 (where N = # ounces you are carrying).

C = $800—the rough price we paid for our backpacking outfit. You will have to use your own numbers here to see how you compare.

P = the Price you must pay for the gear (in dollars, pesos, rubles, etc.) per pound

So the final equation reads like this:

P = C/W

Do you want to buy a new tent? What if the new tent weights three pounds?

P= 800/3 = $266.67.

Is that a good deal? Let’s compare that to staying with your old, four pound tent:

P= 800/4 = $200.00

Is paying $66.67 worth it? Maybe. Most of us would agree that paying $20 would be worth it, if we could save a pound on our pack weight. Many of us would pay a lot more for that!

What about a new 1.5 pound tent?

P= 800/1.5 = $533.33

That makes some lightweight gear seem like a screaming deal!

Now let’s look at my own list, bearing in mind that we are NOT ultralighters, and that my wife and I certainly believe in some creature comforts. So we carry about fourteen pounds each, not including water and food.

P = 775/14 = $57.26 cost per item per pound.

So I am presenting that as the BTS (Backpack the Sierra) constant. Let’s round it off to a nice round $60 per pound.

So how does your pack stack up? The real goal here isn’t to get the pack weight to zero—it’s to see how cost effective your kit is. Do you get by with lower cost equipment, but stuff that might weigh a little more? Or do you go for the ultimate lightweight gear, even if it costs you more?

And how do those answers fit into the equation? I would assume that other regions, which require more or less equipment, have somewhat different answers. Our own answers for winter camping would be like this:

P = 1000/18 = 55.55. That’s pretty dang close to the BTS constant!

[David Thomas]

I'd suggest that what you really care about is not absolute price/pound but the cost of SAVING an additional pound. A theoretical example:

W1 = five pound pack, P1 = $200

W2 = two pound pack, P2 = $350

(W2-W1)/(P2-P1) = 3 pounds saved / $150 spent or

(P2-P1)/(W2-W1) = $50 per pound saved. Which would be a very high-yield choice.

Alas, you usually already have the non-UL gear, so the entire purchase price of the new item has to counted (less anything you can get for the used, heavier gear).

One downside of this approach is that you tend to compare one cheaper, heavier thing for a lighter, more expensive thing. Whereas the big weight savings are when you switch to an entirely different paradigm: Tarp instead of tent. Or no-cook menus instead of stove+pot+fuel.

The cheapest, lightest option is the stuff you don't buy and carry in the first place!

[David Drake]

>"Whereas the big weight savings are when you switch to an entirely different paradigm"

+1 David Thomas.

In my experience, it's a myth that UL is necessarily more expensive. Tarps are cheaper than tents. Low volume frameless packs are cheaper than 80L full suspension monsters. Alky stoves (bought or MYOG) are far cheaper than white gas stoves. Trail runners are cheaper than full leather Goretex boots. Aquamira is cheaper than a pump filter. Etc, etc. True, UL down sleeping bags or quilts come at a premium, but that's as much an increase in quality as a decrease in weight.

Leaving unnecessary stuff behind (usually a big drop in weight from traditional to lightweight kits) cost nothing at all.

At a guess, I'd say my current 3 season list cost significantly less than the OP's, although a fair amount of that savings is MYOG.

[Keith Bassett]

+1 w/ David also. It is the saved lb that we care about.

Alchy stoves, gatorade bottles, creative re-use of household stuff like boil in bags vs extra pots, etc.

That case seems to not fit very well with the big 3 paradigm. Though purchased stoves would seem to be EVEN more expensive per pound saved as you go from al to ti.

Nice to see a swipe at expressing this, hopefully this thread will run to some logical awesome algorithmic conclusion. I have often wondered about this.

[Walter Carrington]

This is a variation of the 'Knapsack Problem'.
http://en.wikipedia.org/wiki/Knapsack_problem

[Paul Wagner]

David, I have to admit that I thought of you half-way through writing the original post. It seemed like something you would have some insight into…

And yes, I made some of our gear, which affects our weight as well. But we also take our comforts: a pair of Crocs for each of us as camp shoes and water shoes, my wife takes a book or two, I take fishing gear. Shoot–we each take a full-size NeoAir, and my wife adds a Z-rest to that for extra padding!

Not UL by any means. But then again, at our age we pretty much get to do what we want, don't we? grin

[Michael Levine]

My version of this when converting to UL was to weigh my current gear, next to it place "the ideal item weight" (essentially what I would buy given a bigger budget than I have), the next column is *my item weight – new item weight* to get weight savings in ounces. The next column was price of new item. The last column was weight saved divided by number of ounces.

So essentially I figured out the cost per ounce saved of every item I wanted to buy. I think it's a pretty legit way to figure out what you ought to buy. $60 for a 1oz savings on a headlamp ($60/oz)? No thanks. $300 on a 12oz weight savings for a quilt($25/oz), much more reasonable.

What that doesn't figure out in is that you can often re-sell old items, but then you ought to figure in your time cost too. You could conceivably, though I didn't, make the price column of the new item be less the cost of your trade-in. That'd make it the most ideal to my mind.

[David Thomas]

Paul, luxury and comfort items are great, IMO. Trimming base weight makes taking those items easier/possible. Crocs are pretty light (if not compact) and can make a cold-water, cobble-filled creek more easily passable. Books for her and fishing for you I might put in the "essential mental-health supplies" category, wouldn't you?

[David Thomas]

Michael, You said it better than I did (and with fewer equations!).

We can blinded by percentage savings in a particular item and the headlamp example you gave is a good one. $$ on incremental savings on small items should be done if it's fun to pursue and you have the budget. But looking at actual dollars per ounces saved so objectively will knock that base weight down much more quickly, given a finite budget.

[Paul Wagner]

Hi David

I am not sure they are mental health items….but they certainly give us joy. And while I am in the wine business, we usually don't take wine on our trips. But if someone brought a small bottle of hootch with them, I would put it in that same category—not part of your base weight, more along the lines of entertainment…

[Bill Segraves]

David's post perfectly anticipated my reaction to the initial question – it's the marginal cost of shaving a given amount of weight that matters if you're thinking about potential gains quantitatively. (This is for otherwise equivalent items. There are other ways of getting lighter, such as changing the type of equipment, that might actually be less expensive, but that tends to lead to lead less general and more complex equations.)

In the realm of decisions made by mainstream competitive amateur and other enthusiast cyclists, $1/gram tends to be the cost of shaving weight. Having spent some time in that world, I wondered whether there might be a similar generality in lightweight backpacking. To test it, I graphed out the cost of various sleeping bags and got pretty much a straight line at $10/ounce through most of the mainstream range. This has seemed to hold pretty true as I've looked at other items, including packs etc.

Not everyone will necessarily find that $10/oz or thereabouts is the right marginal cost for them – for some it's worth paying even more to shave off that last little bit, others will choose to stop with lower-hanging fruit. But knowing where the breakpoint tends to be makes it much easier to make quantitatively driven decisions about whether the ligher of two similar items is worth the extra cost.

Best,

Bill

[M B]

Anything under 10$/oz saved is a bargain, it rapidly rises to as much as $50/oz the lighter you want to go.

The most savings will be realized by purchasing very light gear the FIRST time, and not having to replace it.

[David Drake]

Over the last 4-5 years, I've replaced everything I used to hike with (apart from a couple Platy bladders). I'm pretty careful about buying gear, and try to make a fair amount of stuff, so the total I've spent is only around $1500 (not including clothing items I also wear around town, and would have bought anyway). That includes a couple different pack, sleep and cook options.

My 3+ season base weight has dropped from around 25# (~18# in Big Three alone) to less than 10#, or about $100/ lb. saved ($6.25/oz) for my whole gear closet. But the SUL kit I'm trying for the first time next weekend is only about $670 of that amount, or 670/20= $33.50/lb (~$2/oz).

[M B]

for instance:

have a 40 oz bag, want a 20 oz WM summerlite bag that is $365, cost = $18.25 per oz.
have a 64 oz tent, want a 17 oz hexamid with cuben groundsheet , cost is $540 = 11.5/oz

but if you have 32 oz bag to start, that 20 oz bag cost you 365/12 =$30/oz to save
If you have a 30 oz tarptent, the hexamid cost you 540/(30-17)=41/oz to save.

the lighter you are, the less weight is saved by new $$$ gear, and the higher the incremental cost is to save each additional oz.

[David Drake]

Sure, MB–thought about that after I posted. Fortunately (thanks to advice from this site) almost nothing I've bought was to replace something already pretty light, eg, my 19 oz 40* quilt doesn't replace my 29 oz 20* bag, it's just used for different conditions. Of course, if I want to replace that quilt with a lighter 40* quilt, it'll prob. cost upwards of $50/oz.

As you say, the best value is buying light the first time.

My sense of the OP was there was an assumed premium for going light(er), and that super light=super expensive. My point was, for those of us who can take advantage of the R&D of early adopters, even SUL can be affordable.

[Paul Wagner]

In fact, one of the things I tried was to put together the equipment I used forty years ago to go backpacking: A cheap external frame pack that didn't weigh much more than three pounds, a tube tent that checked in at under a pound, and a Dacron II bag that probably weighed about four pounds. So the big three were under eight pounds. No water filter–we drank straight from the streams. No stove, we just built a fire every night.

I bet if I could find that whole kit at a yard sale somewhere, I could buy the whole thing for under $50. And my cost per pound would be close to $2. That's a great deal…and we had a ton of great adventures with that equipment~!

[David Drake]

Sorry, I misunderstood. No offense meant.

[Paul Wagner]

Grin

[Nick Gatel]

Missing components…

An Esbit stove is about as light as you can get. What is the cost of fuel per liter of water boiled for Esbit, canister, WG, alcohol.

What is the cost per mile of a shoe. Some shoes last less than 500 miles. Boots can last over 2,000 miles and can be resoled.

How long does a pack last? My sub 3lb Kelty has over well over 5,000 miles on it.

etc.

[Ken K]

>> My version of this when converting to UL was to weigh my current gear, next to it place "the ideal item weight" (essentially what I would buy given a bigger budget than I have), the next column is *my item weight – new item weight* to get weight savings in ounces. The next column was price of new item. The last column was weight saved divided by number of ounces. So essentially I figured out the cost per ounce saved of every item I wanted to buy.

This is EXACTLY what I've done since joining this community. Using this spreadsheet, I've prioritized my purchases, and determined opportunity-prices that maximize my "weighted dollars". The $150 10 ounce down jacket didn't make the cut, but the $40 13 ouncer did. SMD Traveler cost $3.90/ounce saved. The next big purchase (a tent) will run $4.00/ounce saved.

After that, I need to start figuring in non-financial issues… That new air pad will run $13/saved ounce, but it also doubles my insulation and may be much more comfortable. Worth it? Or does it still fall behind the $7/saved ounce ti stakes?

This process has been a lot of fun (and addictive), but what kills me is that even with the great values an relatively inexpensive price-per-ounce I've found so far, it completely pales in comparison to just getting my fat butt moving. I lost 50 pounds of "skin in" weight for free! At what point do I stop buying gear and just focus on the health, saving the money for gas money, plane tickets, and park permits?

[Jerry Adams]

"The $150 10 ounce down jacket didn't make the cut, but the $40 13 ouncer did. SMD Traveler cost $3.90/ounce saved."

That illustrates a problem

If you buy the 13 ouncer, you pay less $ per ounce, but then you're left yearning for the 10 ouncer, and if you succumb – you wasted the money on the 13 ouncer

Maybe you're better off buying the best jacket which will last for years, and then eventually you can buy the best pack…

No clear best answer…

[Ken K]

>> If you buy the 13 ouncer, you pay less $ per ounce, but then you're left yearning for the 10 ouncer, and if you succumb – you wasted the money on the 13 ouncer. Maybe you're better off buying the best jacket which will last for years, and then eventually you can buy the best pack… No clear best answer…

That certainly is a concern. In my case, I generally just don't have enough fun money at any one time to validate those really high dollar goodies, and I can generally make myself happy with whatever it is I purchase. In those rare cases that I can buy something now and make an incremental upgrade later, I consider myself blessed. Since all of my retired gear gets passed on to someone else (son, scouts, etc.), it's never a waste.

[Greg F]

I did the same as above with the spreadsheet and calculating dollars saved per ounce. But first i made a plan to hit a 10 pound pack once everything was bought. Then i purchased each item in order of lowest cost per ounce. This way I would never have to re buy to meet my goal

[M B]

…..cannot….help….self….must …..purchase….lighter ….gear.

[A B]

I use this formula, that is I calculate the difference between the new and old price and divide that by the number of grams saved. If you are going for straight weight savings, you'll buy the stuff that has the highest number first.

https://docs.google.com/spreadsheet/pub?key=0AjvbVPeRAFHrcDRaNWhrWFZiQWJFTzdrY0RMelFTQ3c&output=html

Its only calculated for my pants but you get the idea.

But the real issue is that you actually have other things such us a durability, features etc. Its hard to quantify them.

[Author]

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