Wednesday, May 25, 2011

How Many Coins in a Coffer Revisited

I’ve been thinking about the space/weight capacity of carrying coins. If the players come upon a dragon horde of 500,000 assorted coins the players can’t just grab them all and head for the nearest town. After reading the article “How Many Coins in a Coffer” by David F. Godwin from Dragon magazine #80, which is full of cubic centimeter, weight in grams for the various metals and enough math that made my head hurt. But after reading, and the coincidence of me having to roll a ton of coins I’ve decided to make it as simple as possible, 10 coins = a pound. Please no arguments about math. I have a very low tolerance for such nonsense.

So a 20 pound sack can hold 200 coins, 40 pound sack can hold 400 coins. In these cases it’s the weight not the space it takes up. For something like a portable hole or bag of holding it would be how many could fit, not weight. Portable hole at 10’ by 10’ by 10’ and using the square inchage and generalizing that that 4 coins can fit in a square inch. A 10’ square room has a total of 1,728,000 square inches, times that by four that means if the coins are stacked perfectly 6,912,000 coins could fit. But they aren’t going to be stacked perfectly so I guesstimate that you lose 15% space through tossing coins in so that would leave room for 5,875,200 coins which I would round up to 6 million.

So a quick calculation of coins that takes up space if weight doesn’t matter. Like the big ass treasury chest. Again we are using the assumption that 4 coins will fit into a square inch.

A 1 foot square box can fit 6912 coins stacked well round up to 7000. Messy 5872 or 6000.

I’m going to say an average coffer is 8” by 11” by 6” would hold 2000 coins.

A small chest is 18” by 12” by 12” can hold 10,000 coins.

A large chest 48” by 36” by 24” can hold 160,000 coins.

As stated above sacks, bags and backpacks are limited by weight more than space. Exceptions being the magical items that specialize in storage. Enough math for the day. It hurts my head.


  1. Then it's a good thing you don't have to worry about actually physically carrying the coins...

  2. Good going. Useful knowledge and hard-won!

  3. Well, don't hurt yourself, Love. I need you good and strong for our staycation.


  4. The only issue I have is 10 coins per pound. It little more than an ounce of precious metal per coin. That is a lot of metal and makes for a huge coin. I would go with 250, 200, or 100 coins per pound.

    Otherwise the volume info and math looks good at four coins per square inch.

  5. I like that a 1' cube box filled with neatly stacked coins would weigh about 700 lbs (plus the weight of the box itself).

    Meaning that the weight and not the size of the coins is once again the primary limiting factor in how much can be hauled out :)

  6. You see this without going into specific gravity and all that crap in Dragon #80.

    Look at your 1 foot square box.

    A 1 foot square box can fit 6912 coins stacked well round up to 7000. Messy 5872 or 6000.

    At 10 per lb that box would be 600 lbs! At 250 per it would be 24 lbs, 200 per 30 lbs, at 100 per it is 60 lbs which seems to be a reasonable weight a wooden box could contain without being crushed by the weight inside.

  7. @rob:

    A groat in 1300 weighed about 6 grams, meaning that you could say 100 coins per pound and not worry too much (though it might be overestimating the sum a bit--the real mathematical total would be around 75).

    Remember that coins got lighter with time, so if you're going for a more very-early-modern feel in your game, you might say 50 or 75 coins to a pound, whereas if it's late renaissance-style maybe go for 200 or 250.

    Personally I use 10 coins to the pound in my Labyrinth Lord game, just because I want my players to have to think about the logistics of getting treasure out in addition to how to kill monsters and pass hazards.

  8. I've just read the same article, in Best of Dragon Magazine V.

    Glad someone is trying to make sense of it.

  9. Not that I don't want to get into too much detail, but the size of the coin makes a difference in all three. Using tn is just easier in my head.

    I would be intested to see how many quarters, dime and pennies ar in a pound. And throw in half dollars for large size coins. I know I don't want to get too detail just a curiousity.

  10. 181 pennies /lb
    200 dimes/lb
    80 quarter /lb

    the density of gold is over twice that of the metal of US Coins. So halve the above number to find out the precious metal equivalents.

  11. For interested Wikipedia is a good place to start.

    Gives the dates of use. The two main coins are the silver penny and gold florin. The Penny is roughly 1.5 gm or roughly 300 to a lb, and the size of a dime. The Florin is 3.5 gram or 130 to a pound, and the size of a US penny.

    My dad has a silver penny from the reign of King John and it quite small.

  12. All this and your brain didn't explode? Did Wiggy do the math?