D&D 5E Coin sizes

[77IM]

Do you wonder what size coins are? I sure do! Keeps me up at night.

So let's math this out a bit.

50 coins weigh 1 lb. so that means 1 coin is 0.32 oz., or 9 g if we are being metric, which we are, because that is how Wikipedia lists coin weights. So, looking to see if any US coins weigh 9 g, it looks like the closest is the dollar coin, at 8.1 g.

The dollar coin is comprised primarily of copper, so BAM, that's about how big a copper coin is. Actually it will be slightly bigger, about 12% bigger by volume, which is pretty negligible. For those of you unfamiliar with the dollar coin, it is is about an inch across (26.5 mm) and 2 mm thick, so it's not that much bigger than a quarter.

Now let's look up metal density. Copper is about 9 g/cm^3, and silver is 10.5 g/cm^3, so pretty close. This means a silver coin is slightly smaller than a copper coin. Since the copper coin is slightly bigger than the dollar coin, this means that the silver coin will be about the size of a dollar coin, or maybe a bit smaller. I'm to lazy to bust out pi*r^2 and figure out exact sizes for these coins so I'm satisfied saying "both silver and copper coins are about the size of a US dollar coin."

Also, this assumes the metal is pure, and it's usually not. Silver usually has some copper in it, and copper coins (in the US) often have substantial nickel in them, and once you start putting zinc in there things lighten up considerably. So all these sizes are going to be approximate anyway.

Looking at the density of gold (19.3) and platinum (21.5) it looks like they are pretty similar and both nearly double the density of copper and silver! Well that's handy. It means that gold and platinum coins should be half the volume of the copper/silver coins.

Since most US coins are copper, a gold or platinum coin of the same dimensions would weigh twice as much. So to get the dimensions of a 9 g coin (50 coins weigh 1 lb. in D&D), we need to find a 4.5 g coin. Crawling around Wikipedia, it looks like the closest is the familar US nickel coin, at 5 g. That's actually OK, because our D&D fantasy coins are probably not pure gold or platinum, which means they will be less dense and therefore slightly larger than a pure coin.

So there you have it:
A copper or silver piece is about the size of a US dollar coin.
A gold or platinum piece is about the size of a US nickel.

 

[The Grassy Gnoll]

So, for us Brits, that's a copper/silver coin = 10p piece, and a gold/silver = 20p piece. More or less. That sound about right?

Poor old electrum. Never gets invited to the party.

 

[Beleriphon]

So, for us Brits, that's a copper/silver coin = 10p piece, and a gold/silver = 20p piece. More or less. That sound about right?

Poor old electrum. Never gets invited to the party.

Its because electrum gets drunk and makes inappropriate jokes about astral diamonds all night.

 

[77IM]

Wikipedia says the 20p piece is 5 g so that sounds about right for gold/platinum. It looks like the 10p piece comes in different weights so I'm not sure about that one. You are looking for a coin that is primarily copper and/or nickel and weighs about 9 g.

It's worth noting that the gold/platinum piece is about the size of a nickel or 20p piece, but WEIGHS TWICE AS MUCH, so it would feel more solid in your hand than those other coins.

I wonder if the people who make those metal "campaign coins" have taken this into account? It would be fun to buy some gold pieces and say, "Well these are brass-plated lead, but it's the exact size and weight of a D&D gold piece."

 

[77IM]

Also, I am starting to think that for 5e they should have thrown out the sacred cow of "50 coins = 1 lb." and gone with the more decimal system of "100 coins = 1 lb."

1. It makes the math easier when you plunder the dragon's hoard. "17,600 total coins... that's only 176 lbs., we should be fine."

2. It allows you to introduce the 1-lb. gold bar as the next unit of currency (worth 10pp, 100gp, etc.).

3. It makes all the coins slightly more realistic (everybody lol @ "realism in D&D") since 5 g of gold is kind of a lot. The price of gold fluctuates but right now it looks like 5 g of gold is worth about $200. If the gp weighed half as much, it would be worth about $100. And actually, if you look at the prices of common items (meals, clothing, staying at the inn, etc.) I think that it's a helpful guideline to think of a gp as worth about $100.


If you cut the weight of coins in half, then the copper/silver coin is slightly smaller than a nickel, and the gold/platinum coin is about the size of a dime, or a penny if the metal is less pure.

 

[Beleriphon]

Also, I am starting to think that for 5e they should have thrown out the sacred cow of "50 coins = 1 lb." and gone with the more decimal system of "100 coins = 1 lb."

I'm fairly certain that this is how it was until 3E, but my 2E books are in storage so I can't confirm that for sure.

1. It makes the math easier when you plunder the dragon's hoard. "17,600 total coins... that's only 176 lbs., we should be fine."

2. It allows you to introduce the 1-lb. gold bar as the next unit of currency (worth 10pp, 100gp, etc.).

3. It makes all the coins slightly more realistic (everybody lol @ "realism in D&D") since 5 g of gold is kind of a lot. The price of gold fluctuates but right now it looks like 5 g of gold is worth about $200. If the gp weighed half as much, it would be worth about $100. And actually, if you look at the prices of common items (meals, clothing, staying at the inn, etc.) I think that it's a helpful guideline to think of a gp as worth about $100.

I like that quite a bit, it does make the math easier. That said, it does make a big hoard seem somewhat more impressive in terms of sheer mass.

If you cut the weight of coins in half, then the copper/silver coin is slightly smaller than a nickel, and the gold/platinum coin is about the size of a dime, or a penny if the metal is less pure.

Hmmm, interesting.

 

[bganon]

The gp/sp/cp values are hard to connect to real-world values since historically the price ratio is much closer to 100 for each step than 10. In fact, right now it looks like gold is 74 times more valuable than silver, which is 86 times more valuable than copper.

I rather like having 10,000:100:1 ratios in D&D, but it does mean repricing everything off of a silver (or even copper) standard. It does make for a lot less gold carried around.

And in the real world platinum is actually worth slightly less than gold, nickel and tin worth several times copper, etc...

 

[delericho]

I'm fairly certain that this is how it was until 3E, but my 2E books are in storage so I can't confirm that for sure.

In 1st Ed (and BECMI) encumbrance was actually in coins. 2nd Ed switched to pounds; I wasn't able to find a weight for coins in that edition, but 100 rings a bell.

FWIW, the UK £1 coin is roughly 50 to a pound, so that's a good rule of thumb for me. 100 to the pound is ridiculously light, especially if the coin is made of gold.

Realistically, though, the weights probably shouldn't be fixed - not only because the metals themselves will vary wildly in purity, but also because the coins won't be manufactured to any standard process - indeed, a "gold piece" may well mean something very different from one end of the contient to the other. There's no reason to think that 10gp the party just found in that ancient temple bears any real resemblance to the coins they've grown up with.

 

[The Grassy Gnoll]

I'd say a gold/silver piece would be about a £1 coin then. Cheers!

 

[Tony Vargas]

I'm fairly certain that this is how it was until 3E, but my 2E books are in storage so I can't confirm that for sure.

In 1e, coins were 10 to the pound. Yeah, they were big. IIRC, there was a dragon article doing all this stuff - the writer decided all coins were the same diameter, but different thickness, to deal with the different metal densities. Of course, that was a long time ago, I could be very wrong....