Pennies are cheap, but tacos can be expensive
July 28, 2010 9:33 AM   Subscribe

How many pennies fit in a 1 lb coffee can?

My boyfriend is an inveterate penny purger. He just throws them in the garbage! This wounds me in my penny-pinching soul. So, a year ago I made him a bank from a 1 lb coffee can and insisted that he use it. The deal was, if we could dine on the worth of the contents, he would cease his wasteful ways.

Well, the can is nearly full and tonight we have a dinner date with the coin machine. But where will we eat? Will we be dining off the Taco Bell Value Menu (as he insists)? Eating at the taqueria? Or ordering appetizers, margaritas and flan to go with our fine sit down Mexican meal?

Just how many pennies fit in a 1 lb coffee can?
posted by annaramma to Work & Money (65 answers total) 22 users marked this as a favorite
 
Can you take it to the bank and see what they give you for it?
posted by Jaltcoh at 9:34 AM on July 28, 2010


Umm... Won't the coin machine tell you how many pennies fit in the can? This sounds like a hypothetical question.
posted by antifuse at 9:36 AM on July 28, 2010 [1 favorite]


This Yahoo Answer has a breakdown of how many pennies are in a pound, so perhaps you could weigh the jar to get a ballpark idea of how much money is in the jar?
posted by ThePinkSuperhero at 9:37 AM on July 28, 2010 [3 favorites]


Yeah, just take the silly can to the Coinstar machine and then look at the totals.
posted by Burhanistan at 9:37 AM on July 28, 2010


If you can, go to your bank and use their coin machine. The coin machines in grocery stores have fees, or force you to get your cash out in the form of iTunes gift cards or something.

As to your question, I guess you'll find out soon enough right? If you want to have a guess at it, do you have a scale? Pennies before 1982 weigh 3.11 grams. After 1982, 2.5 grams.
posted by fontophilic at 9:39 AM on July 28, 2010


I don't have a pound coffee can but I do have a 326g one. I can get 20 pennies in one layer. The can is about two rolls tall, so that'd be 40 rolls or $20. With your bigger can I'd guess about $30.
posted by seanmpuckett at 9:39 AM on July 28, 2010 [1 favorite]


Do you have a bathroom scale? You can weigh it. Pennies are about 3 grams each, so a pound of pennies is very roughly 150 pennies.
posted by backseatpilot at 9:39 AM on July 28, 2010


"a penny's volume is .360 cubic centimeters and the mass is 3.1 grams (pre-1982) and 2.5 grams (after 1982)"* The volume of a can of coffee is about 170 cubic inches*. 16.38 cubic centimeters in one cubic inch*. coffee can is 2784.6 cubic centimeters. 7735 pennies.

Seventy seven dollars. This is all internet math but I bet it's close.
posted by jessamyn at 9:41 AM on July 28, 2010 [1 favorite]


Oh, or if we're taking wild guesses, I'm gonna say you have about $27 and change.
posted by fontophilic at 9:41 AM on July 28, 2010


Do you have a bathroom scale? You can weigh it. Pennies are about 3 grams each, so a pound of pennies is very roughly 150 pennies.

The problem is that coffee and pennies have a different density, so they occupy different amounts of volume at the same weight.
posted by griphus at 9:41 AM on July 28, 2010 [1 favorite]


A couple minutes of Googling tells me that a one pound can of coffee holds 3.92 cups, which is equivalent to 927 cubic centimeters, and that the volume of a penny is .360 cubic centimeters. And 927 divided by .360 is equal to 2,575. So you have $25.75 in that can!

I can't really vouch for the accuracy of any of that data, though -- I just used the first hit for each search. So, yeah, take it to the bank, see how much they give you, and then come back and tell us!
posted by magnificent frigatebird at 9:42 AM on July 28, 2010


I'm sorry, I should have specified that I'm just antsy and curious. Of course I'll find out tonight, but I was just wondering if anyone had an educated guess or anecdotal information to share. Googling for information on coffee cans of pennies came up with a lot of information about the weight of pennies and some terrible math.
posted by annaramma at 9:43 AM on July 28, 2010


Apparently pennies have a packing density of about 60%.
posted by ecurtz at 9:43 AM on July 28, 2010 [2 favorites]


jessamyn: You don't seem to account for the packing problem.
posted by seanmpuckett at 9:43 AM on July 28, 2010


Penny's volume = .360 CC. V of coffee can = 729.65877 CC sq. Pennies to fit in coffee can = 2026 = $20.06
posted by Think_Long at 9:44 AM on July 28, 2010


Yeah, that assumes a perfect packing density. So less than $20 - I think you're going to be dining at Taco Bell tonight. I am truly sorry.
posted by Think_Long at 9:45 AM on July 28, 2010


Based on my water cooler bottle full of coins, I am going to estimate you are going to have about $24.67
posted by JohnnyGunn at 9:45 AM on July 28, 2010


This doesn't answer your question, but the thrill of the unknown should be part of the fun! Kind of like Wheel of Fortune.
posted by amethysts at 9:46 AM on July 28, 2010


If you average the weight of the pennies between pre-1982 and post-1982, a penny weighs 2.805 grams.

There are 453.59 grams in 1 lb.

453.59 / 2.805 = ~162 pennies.

Enjoy your $1.62 meal.

(And to stop being flip for a moment, wasting perfectly good money is not something I'd advocate, but maybe he should just use it to get two bucks back once a year while grocery shopping or something.)
posted by asciident at 9:46 AM on July 28, 2010


The problem is that coffee and pennies have a different density, so they occupy different amounts of volume at the same weight.

I realize that the "1 lb can of coffee" will weigh significantly less than the same can filled with pennies. The volume is inconsequential, since you're talking about a can filled with pennies. Weigh the can (or weigh yourself with and without the can and take the difference) and then multiply the pounds by 150 and you should get a rough number of pennies.

Seventy seven dollars.

I think that might be way too high, since the pennies don't pack perfectly (you don't have a solid slug of penny sitting in the can). I'd guess between 30-50% of the volume of the can is empty space.
posted by backseatpilot at 9:46 AM on July 28, 2010


My bad, packing problem is critical here.
posted by jessamyn at 9:47 AM on July 28, 2010 [1 favorite]


453.59 / 2.805 = ~162 pennies.

Again, that's how many pennies are in a pound, not how many pennies can fit in a 1-lb coffee container. It's a problem of volume, not mass.
posted by griphus at 9:47 AM on July 28, 2010


And thinking about it more, you're not going to have 1 lb of pennies nor perfect packing density, so at a guess I'd say you have something closer to $10, but it still seems like a perfectly good compromise to just use it as a yearly grocery discount or similar since it took so long to build up that amount!
posted by asciident at 9:49 AM on July 28, 2010


Others have pointed out that there's going to be a lot of empty space, but isn't the amount of space variable based on how the pennies are stored? If they're careful to economize the space by setting the pennies layer by layer, that's different than if they throw the pennies in the can and let them land diagonally.
posted by Jaltcoh at 9:50 AM on July 28, 2010


Dang it, you people, stop being so quick.

Here's my rough math:

3.92 cups in a one pound coffee can (not confirmed, via quick googling)

Call it 4 cups, that gives you 64 fl oz, which gives you 1893 ml.

one penny volume = .36 ml

Which tells me that if you melted them down, you'd be able to fit $52.58 in pennies into the coffee can.

Times 60% to account for extra space when packing (thanks, ecurtz) = $32.55.

Ballpark? somewhere in the twenty/thirty dollar range. Let me know when this involves jellybeans.
posted by gimonca at 9:50 AM on July 28, 2010


We need the dimensions of the coffee can.
posted by reductiondesign at 9:52 AM on July 28, 2010


The volume is inconsequential, since you're talking about a can filled with pennies.

Wait, why? The volume is is a constant, determined by 1 lb divided by the density of the coffee.

We need the dimensions of the coffee can.

...or the density of the coffee.
posted by griphus at 9:54 AM on July 28, 2010


Assuming the 1 lb coffee can originally held 1 lb of coffee (as opposed to 1 lb of pennies), that means it holds ~ 4 cups. The problem you face is that there can be wildly varying packing factors of pennies in the can. Therefore, the widely-recommended "weigh it" approach is much more likely to be accurate. If you want an estimate otherwise, I can give you an approximate upper bounds:

The maximum packing factor for disks is 0.90, and if things were packed as densely as possible, that corresponds to ~ 2300 pennies, or $23. In practice, I would guess probably 70% of that (it's a guess), so $16. Taqueria it is?
posted by JMOZ at 9:54 AM on July 28, 2010


if you're super antsy, could you wrap your pennies and count them at home? (i actually find wrapping coins a soothing activity)

alternately, count out some easily measured proportion of pennies then multiply to find the total amount.

a lot will depend on how full "nearly full" actually is. do you shake it down to compress the volume? or do you just toss haphazardly?

(as an aside, i'm completely aghast that your bf actually throws pennies in the garbage. at least put them in the take-a-penny jar for people... or donate them to the salvation army... or save them for street musicians)
posted by watch out for turtles at 9:55 AM on July 28, 2010 [1 favorite]


FWIW, I recently cashed in a Pepperidge Farm Piroutte can full of coins (lots of quarters and dimes in there), and it was around $92. I think you'll be lucky to get $30.
posted by Burhanistan at 9:56 AM on July 28, 2010


Thank you for all your guesses!

So somewhere between less than $20 - $77.35 . . . I'm thinking the $25 ballpark is probably pretty close. That gets me out of Taco Bell, but probably not to margaritas.

Yeah, I was hesitant to include the "1 lb" detail because it sounds like I'm talking about 1 lb of pennies, but of course the can hold much more than that. gimonca, your ballpark sounds pretty good to me.

amethysts, there is a fun "Wheel of Fortune" aspect to it, isn't there? I'm hoping the results will convince the boy to literally stop throwing his money away, but a nice meal would be far more convincing than Taco Bell.

I promise to report back. Oh, and I'll send a present to the person with the best guess.

Trust me watch out for turtles, if he wasn't just the best thing since sliced bread, I would question his character!
posted by annaramma at 9:59 AM on July 28, 2010


gimonica's calculation was off by a factor of 2, but the technique is right.

You're going to have $12.50 to $16.00 depending on the volume of the coffee can. My guess is $13.73.
posted by ecurtz at 9:59 AM on July 28, 2010


gimonica- 4 cups is ~946 mL, NOT 1893 mL. That factor of 2 brings your estimate more in line with others (like mine): $16.
posted by JMOZ at 10:01 AM on July 28, 2010


Doh!, gimonca's calculation - sorry I need to remember to copy & paste user names!
posted by ecurtz at 10:04 AM on July 28, 2010


For the record: my guess is $12 - based on 60% of my original estimate of $20.06.
posted by Think_Long at 10:10 AM on July 28, 2010


Suggestion: Save ALL your change in the can at the end of every day. Every 18 months or so I cash out $300+. Not a bad payoff for doing nothing.
posted by coolguymichael at 10:11 AM on July 28, 2010 [1 favorite]


My boyfriend is an inveterate penny purger. He just throws them in the garbage!

I think the real question is ... how many pennies are being thrown away on average? What is the effort level in throwing them away vs. saving them and then redeeming them for usable denominations? A trip to the grocery store to use Coinstar takes time, energy and money, both in gas and the service charge. Rolling your own takes even longer.

Your boyfriend may actually be efficiently managing his time.
posted by Cool Papa Bell at 10:23 AM on July 28, 2010


Actually it would be easy to figure out the exact value without counting. Fill the can with water (with the pennies in it). Pour the water off and measure it's volume. Subtract this from the volume of the can and multiply by 0.36 ml then...Eureka!
posted by tallus at 10:31 AM on July 28, 2010 [2 favorites]


I had written out a long answer based on a change can I had, a bit smaller than a coffee can, which had about $180 worth of change when filled with a mixture of coins, and trying to extrapolate from that to pennies alone using some highly questionable assumptions. That was before I saw some of the other, much better methods of estimation posted here. Suffice it to say that my estimate came out to about $33.
posted by DevilsAdvocate at 10:33 AM on July 28, 2010


A trip to the grocery store to use Coinstar takes time, energy and money, both in gas and the service charge.

Unless you occasionally go to the grocery store anyway, in which case you're only losing the service charge and the 3 minutes it takes to cash the pennies in.
posted by coolguymichael at 10:34 AM on July 28, 2010 [1 favorite]


The volume estimates are nice, but I wonder if the mathematically inclined in the audience know if circle packing theory has anything to say on the subject of best organizing pennies in a coffee can.
posted by pwnguin at 10:35 AM on July 28, 2010


Someone asked a similar question at Yahoo! Answers, although this is hardly a reliable source.

Seriously, though, Wikipedia says that a US penny has diameter 0.750 inches and thickness 0.061 inches; you can compute that the volume of a penny is about 0.027 cubic inches. A 10-ounce coffee can, which I have, is four inches in diameter and 5.25 inches tall; this is 66 cubic inches. Assuming that 1-pound coffee cans are packed as "efficiently" as 10-ounce ones, a 1-pound can has volume about 66*1.6 = 106 cubic inches.

Dividing this estimated volume of a coffee can by the volume of a penny gives about $39.

But this doesn't take into account the gaps between pennies. It is known that, for example, 20 circles of radius 1 can be packed into a circle of radius 5.122, which means they'd take up 20/5.1222 of the space, or about 75%. Let's say that randomly-thrown-down pennies take up 70% of the space, which I admit I just made up.

So you have about 70% of $39, or $27.
posted by madcaptenor at 10:37 AM on July 28, 2010 [1 favorite]


pwnguin: I'm not sure. It should be noted that the best way to store pennies in a coffee can is to go trade them in for real money. Or tacos.
posted by madcaptenor at 10:38 AM on July 28, 2010


Subtract this from the volume of the can and multiply divide by 0.36 ml then...Eureka!
posted by DevilsAdvocate at 10:38 AM on July 28, 2010 [1 favorite]


Also, under reasonable assumptions about randomness, if you throw all your coins in a jar at the end of the day then a kilogram of money weighs about $28.58. I figured this out one day a few summers ago when I was bored.
posted by madcaptenor at 10:40 AM on July 28, 2010


pwnguin: my 90% figure is for circles filling a plane. Circles filling a larger circle will be somewhat smaller and is certainly an example of circle packing theory. One can safely assume that it will be less than 90%, but depending on the relative diameter of the pennies to the can, it can be trivially smaller or MUCH smaller. (consider the case, for example, of a can with diameter infinitesmally smaller than twice the diameter of a penny. In that case, the packing factor will be just over 25%.)
posted by JMOZ at 10:41 AM on July 28, 2010


(Of course, in that case, the optimum 3D packing structure will be quite different)
posted by JMOZ at 10:42 AM on July 28, 2010


Never mind idle speculation. I have actual data. I have taken 32 oz yogurt containers filled (in the normal, haphazard way) with sorted coins to the Coinstar machine and this is what I got (all figures approximate):The figures for dimes and quarters are not typos.

According to this, a 3lb coffee can is approximately 12 - 13 cups, which jives with the previous estimates of approximate 4 cups of volume in a 1lb coffee can. The 32 oz yogurt container is also approximately 4 cups, so I can say with fairly high confidence that your coffee can of pennies is somewhere in the $12 range.
posted by mhum at 10:44 AM on July 28, 2010 [2 favorites]


I had written out a long answer based on a change can I had, a bit smaller than a coffee can... Suffice it to say that my estimate came out to about $33.

And now that I read through the thread and explore a bit online, I realize I was envisioning a three-pound coffee can, so I'd like to revise my estimate downwards by a factor of 3 to $11.
posted by DevilsAdvocate at 10:57 AM on July 28, 2010


Mhum - does that mean that dimes and quarters have roughly the same ratio of packed-volume to value? That's really fascinating.
posted by Pickman's Next Top Model at 11:12 AM on July 28, 2010


Thank you mhum! That's just the kind of data I was hoping to find. Unfortunately, $12.50 is bordering on Taco Bell territory.

Luckily, my bank counts coins for free. We won't have to sacrifice any luxury at the taqueria.

And madcaptenor, you're absolutely right. The best way to store pennies is to go trade them in for tacos!
posted by annaramma at 11:21 AM on July 28, 2010


[few comments removed - we are not talking about anythig other than pennies-in-a-coffee-can for now.]
posted by jessamyn at 11:47 AM on July 28, 2010


I would say just about every penny. He would sort through his pockets and throw out the pennies. Ack! Just thinking about it hurts me.
posted by annaramma at 11:48 AM on July 28, 2010


Mhum - does that mean that dimes and quarters have roughly the same ratio of packed-volume to value? That's really fascinating.

In my experience, yes. It was entirely unexpected. I got roughly 2.5 times the number of dimes as quarters into the same volume.

One more note: when we say that a container is "full" of coins, there's actually quite a bit of wiggle room in the definition of "full". Is it full when we can no longer put the lid on the container? Or do we call it full when it reached the level of the original contents (i.e.: taking into account the container's headroom)? In the case of pennies, I suspect that you could easily swing your results by 50 cents in either direction by taking more or less strict definitions of "full".
posted by mhum at 12:17 PM on July 28, 2010


annaramma: "....Unfortunately, $12.50 is bordering on Taco Bell territory. "

But you can eat like a king and queen* at Taco Bell for that much money. Value menu? P'shaw!

* To the maximum extent that kings and queens at at Taco Bell; YK&QMV.
posted by JMOZ at 12:59 PM on July 28, 2010


mhum and pickman's: the mass of a quarter is exactly two and a half times the mass of a dime, which I suspect is intentional and dates back to when coins were made of precious metals. So a pound of quarters and a pound of dimes weigh the same. That being said, Wikipedia claims they have the same composition (eleven-twelfths copper, one-twelfth nickel) and the volume of a quarter is not two and a half times the volume of a dime.
posted by madcaptenor at 1:51 PM on July 28, 2010


My question is, why does he throw away pennies, but keep nickels, dimes, and quarters? (I assume he does this.) A nickel is the equivalent of a mere five pennies. But he would keep the nickel, and throw away the five pennies?

I mean, as long as you're going to keep your change (instead of, say, tossing it all into whatever tip jar comes your way) you should keep the darned change.

I have a piggy bank where I throw all my change. Once or twice a year I cash it in at the Coinstar machine, and I'm always surprised how much money it is!

I trust you are going to update this thread later tonight. Else we will all be very cross.
posted by ErikaB at 3:08 PM on July 28, 2010


I'm headed to the bank. I'll let y'all know the results.

Preaching to the choir ErikaB . . . preaching to the choir.
posted by annaramma at 4:15 PM on July 28, 2010


I have a 1/2 gallon jug that I filled with pennies and cashed out a few years ago. It held about $20, IIRC. Half a gallon is eight cups, so each cupful is worth about $2.50.

This page says that "each pound was about 5.43 measuring cups of ground coffee."

5.43 * $2.50 = $13.58, so that's my guess.

disclaimer: I do not understand how math works.
posted by Karlos the Jackal at 4:15 PM on July 28, 2010


madcaptenor writes "So a pound of quarters and a pound of dimes weigh the same."

Did you mean to say that a given dollar value of quarters and dimes weight the same?

madcaptenor writes "Wikipedia claims they have the same composition (eleven-twelfths copper, one-twelfth nickel) and the volume of a quarter is not two and a half times the volume of a dime."

This makes sense if they are considering a coin's volume as being its maximum thickness times its area. Coins are thicker on the edges so the actual volume (measured say by displacement of water) is going to be smaller than that computed value.
posted by Mitheral at 4:51 PM on July 28, 2010


So a pound of quarters and a pound of dimes weigh the same.

Oh wait, I know this one... a pound!

Seriously though, I'm really interested to know the dollar amount, as I have a big can of change as well.
posted by JenMarie at 5:08 PM on July 28, 2010 [1 favorite]


JenMarie: there are 200 dimes or 80 quarters to the (avoirdupois, i. e. "regular") pound. That's $20.
posted by madcaptenor at 5:50 PM on July 28, 2010


It's been (almost) five hours - I demand an update!
posted by deborah at 8:55 PM on July 28, 2010 [1 favorite]


Okay folks, the grand total is . . . $9.36. To be fair, the boy was a little overeager and the can was only about 90% full. That means with his packing style and the size of the can, I would estimate a 1 lb can holds $10.40.

With her guess of $10, I declare asciident the winner!

With the boy promising to save his pennies for next year, I also declare myself the winner!

MeMail me for your prize.
posted by annaramma at 11:02 PM on July 28, 2010 [5 favorites]


What?! Under $10? That's depressing. I was really hoping Jessamyn had the correct answer. Hope you enjoyed your beef jerky and diet cokes.
posted by JenMarie at 12:19 AM on July 29, 2010 [2 favorites]


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