# D&D 5ECoin sizes

#### 77IM

##### Explorer!!!
Supporter
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

##### Explorer
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

##### Totally Awesome Pirate Brain
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

##### Explorer!!!
Supporter
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

##### Explorer!!!
Supporter
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

##### Totally Awesome Pirate Brain
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

##### Explorer
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

##### Legend
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

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

#### Tony Vargas

##### Legend
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....

#### MechaPilot

##### Explorer
What if a "copper piece" is just a value, and you can pay that value with a copper coin the size of a US Kennedy Dollar, with a silver coin the size of a US nickel, or a gold coin the size of a US dime?

#### PeterFitz

##### First Post
I worked out coin sizes a little while ago with the aid of Wolfram Alpha:

These sizes assume a coin thickness of 2mm, at 50 coins to the pound. If you want to use a 100/lb ratio, just drop the thickness to 1mm and Bob's your uncle.

#### 77IM

##### Explorer!!!
Supporter
PeterFitz, that's excellent! Thank you for sharing!

#### The Grassy Gnoll

##### Explorer
Electrum keeps trying to blag to girls at parties that he's "with the band", but everyone knows he's just jealous of his sexier and more musical cousin, plectrum. It's why he drinks.

#### aramis erak

##### Legend
Quibble over the details...

Platinum, pure 21.4 g/cc
Gold, 24k, 19.6 g/cc
silver, 0.999fine, 10.49 g/cc
Copper 8.9 g/cc
tin 7.2 g/cc
zinc 7.31 g/cc

Electrum is a problem - it has 2 common formulations which are gold & silver alloy... but it's defined as 20-80% gold and 20-80% silver, with the balance in base metals (copper, tin, zinc, antimony)
• Lycean: 45-60% gold 35-55% silver, 0-5% base metals
• Anatolian: 70-90% gold, 9-30% silver, trace base metals
• German: 60% copper, 20% tin, 20% zinc

Coin gold is typically 14k, (58%,) with the balance being copper, and a specific gravity of about 15.1g/cc. Lets call this our base worth for gold coin... which is a good thing, since pure gold (24k) is worth about 12 to 20x silver... and this gives about 1 15.5:1 ratio to the silver coin, and thus pure gold worth about 1.55x coin gold

Coin Silver is usually 90% silver, the balance being largely copper; pure silver doesn't wear well enough. Some medieval silver coinage was as low as 50%, usually mixed with tin, zinc and copper. 90% is about 10.4 g/cc... 50% is about 9.7 g/cc

Coin Copper, is almost always alloyed with tin and zinc, and sometimes with gold or silver. But copper's inherent value is about 1/70th that of silver in the medieval era. So, to plus it up, say, 5% silver... if we go with 90 copper, 7.5% silver, 2.5% zinc, we get about the right value, about the right hardness, and about the right brightness, and a historic coin composition. We also get about 8.98 g/cc

Note that the platinum coin, given the generally medieval tech, is anchronistic, and would require magic to work. (developing the ore isn't the problem, despite being essentially victorian; actually working it, however...) So, assuming nearly pure is fine. Setting the value to 10x gold (rather than the current 0.9x) is thus easily justified.

And, for electrum, let's go really debased... 27% gold (worth 0.419 gp), 70% silver (worth 0.07 gp) 3% copper. It's about 12.8 g/cc and worth just shy of half a gp

So, recapping more realistic coin-densities, and 9.07g per coin. 3 figure accuracy
 Platinum coin (magically pure) 21.4 g/cc 0.424 cc 23.2x1mm 19.0x1.5 16.4x2mm Gold Coin Alloy 14k 15.1 g/cc 0.601 cc 27.7x1mm 22.6x1.5mm 19.6x2mm Low Gold Electrum 0.27/0.70 12.8 g/cc 0.709 cc 30x1mm 24.5x1.5mm 21.2x2mm Coin Silver Alloy .900 fine 9.7g/cc 0.935 cc 34.5x1mm 28.2x1.5mm 24.4x2mm coin copper alloy (5% silver) 8.98 g/cc 1.01 35.9x1mm 29.3x1.5mm 25.4x2mm
1.01 cc[/td]

##### First Post
50 coins per pound is a good standard. It gets you coins not unlike a U.S. quarter, which are substantial without being ridiculous (the 10 coins to a pound standard results in coins heavier than a U.S. silver dollar by 50%). Going to 100 coins per pound gets you a coin like the Roman denarius or the Byzantine solidus, which are smaller. I have several ancient denarii, and they compare to dimes, while later coins like the antoninianus (infamous for its debasement; my antoniniani are all heavily blackened) are more physically impressive in size.

So I think 5e is in the Goldilocks zone for fantasy coins.

#### mlund

##### First Post
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."

They should have because it is closer to the classical / middle-ages norm and more convenient. The real-world "Gold Piece" standard of the middle ages was the Roman Solidus, produced by the Roman Empire (Byzantine Empire in modern parlance) in Constantinople. The Solidus originates as a coin of the purest form of gold that could be obtained in a weight of 1/72th of a Roman Pound. The Roman Pound just happens to be 0.72 British/American Imperial Pound. So 100 Classical Solidi is 1 Modern Pound of Gold.

Marty Lund

##### First Post
They should have because it is closer to the classical / middle-ages norm and more convenient. The real-world "Gold Piece" standard of the middle ages was the Roman Solidus, produced by the Roman Empire (Byzantine Empire in modern parlance) in Constantinople. The Solidus originates as a coin of the purest form of gold that could be obtained in a weight of 1/72th of a Roman Pound. The Roman Pound just happens to be 0.72 British/American Imperial Pound. So 100 Classical Solidi is 1 Modern Pound of Gold.

Marty Lund
The solidus is a fine coin. It's about the size of a dime, weighing around 4.5 grams. Its weight is equivalent to the denarius, though due to relative density it's thinner.

The problem with those two coins as standards is that they're quite small. When you imagine a fantasy treasure chest, you don't think of it as full of little dime-sized coins; it has coins with a bit more heft and substance. 9 gram coins are much better; a gold piece that looks like the US dollar coins is a more appealing imaginary treasure. It's not 1e's silly 45 gram standard, where the coins would come out massive.

Really, coins should vary. Actual gold coins were from 3.5g up to more than 10, and some famous silver coins like the Spanish "Piece of Eight" we're big whoppers at over 25g. It can add color to have little or big coins, as long as you consider the overall value based on weight and metallic composition; you could give 36 GP in 72 late Roman solidi, if you wanted.

#### 77IM

##### Explorer!!!
Supporter
Ah, but that's where MechaPilot's fine idea comes into play:

What if a "copper piece" is just a value, and you can pay that value with a copper coin the size of a US Kennedy Dollar, with a silver coin the size of a US nickel, or a gold coin the size of a US dime?

If standard coins are tiny, then you can have coins of the same metal, but one denomination up, and they are only 10x as massive -- which, due to width*pi*r^2, means they are not 10x in diameter, but still fill up a treasure chest nicely!

So now, a merchant may have a few dime-sized gold pieces and nickel-sized silver pieces in his money-purse, but a dragon is laying on a bed of "gold pieces" made of giant silver coins and "platinum pieces" made of giant gold coins. Shiny!

#### MechaPilot

##### Explorer
Really, coins should vary.

As I see it, not only should coins vary, but currency itself should vary. As should the value of various coins and currency.

In my homebrewed campaign setting, called Tenesia (after one of the major land-masses of that world), coins vary in size, shape, character, and value:

One nation mints its coins with the profile image of its current ruler (if you know the history of that nation, you can tell the age of a coin by the ruler depicted upon it).

Another nation mints coins with animals depicted on them (eagles, wolves, buffalo, etc).

Under the sea, the merfolk don't get coinage unless it comes from wrecked ships. Coins are as valuable to them as gems are to those who live above the waves. Instead, they have a system of currency based on sea shells, shark teeth, and pearls.

For the races that live underground, precious metals are cheap. The price of anything is inflated if you try to pay for it with gold, silver, and copper. Instead, they frequently make their valuable coinage from rare alloys, or pay for things with gems (which are still more rare and valuable than gold, silver, and copper).

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