"g.p. weight"

[Festivus]

Someone out there had done the math and analysis on this, I had done some looking for myself to understand it.

http://dnd.madirish.net/?content_id=81

OK, the basic calculation is scalable WRT specific gravity, so if you take this calculation, and multiply the output by the ratio of specific gravity of gold to (silver/copper/platinum), you'll get the right answer for that type of coin, assuming they're all the same size.

Gold Piece to lb:

Density(Au)=19.32 g/cc, 1lb=453.6g, so there's 23.48cc of Au per lb. For convenience, I'm switching this over to mm3. 23480 mm3/lb.

From the PH, we measure the diameter of a gp as 31 mm, so radius 15.5, and π*r2 gives us 754.77 mm2 for the face area of a coin. I assumed a thickness of 3mm (about 1.5 nickels thick), giving 2264.3mm3 per coin, so....

10.37 gp/lb. and just round that to 10, since we're just making up a thickness anyway...

So yeah, it really is 10 gp/lb.

assuming they use the same stamps for everything, and just load different slugs and dies in for different coins:
pp= 9.36/lb. call it 10.

sp=19.08/lb. call it 20.

cp=22.26/lb. call it 20.

The final coin weight table:
10gp = 1Lbs
10pp = 1Lbs
20sp = 1Lbs
20cp = 1Lbs

 

[BOZ]

cool, thanks all, 10 gp per lb it is.

 

[HeavenShallBurn]

Over history coins have been all sorts of sizes. Roman coins were tiny, smaller than modern U.S. dimes in many cases. Then you have the post renaissance coins that the D&D standard is based on and these were larger. Roughly fifty to a pound sounds about right.

Then you have American coins. By the standards of the rest of the world American coins were generally oversized. The ordinary run of penny, nickel, dime, quarter were all the same size back when they were made from silver. That's fairly large. Then you had the gold coins and they were very big too, the largest were the $20 double eagles which were about a half ounce each in some time ranges, and the $50 slug that was a solid ounce.

 

[robberbaron]

Have your coins as heavy as you want them to be.
Seems silly to me to make a poor peasant carry 1lb in his pouch for 10 copper pieces but, if you want your coins to be huge lumps of metal that is entirely your decision.

IMC 50 coins = 1lb.