August 01, 2016

The size and weight of 10,000 gold pieces


I was reading this comic and, being an RPGer, I wondered, "Can 10,000 coins really fit in that bag? And wouldn't that weigh 1000 pounds under the old D&D rules?" So I had my daughter, the resident math genius, figure out if 10,000 coins could fit in a bag that size.

She estimated a coin would be about an inch in diameter and .25 inches thick, which would make a coin's volume be .25 x pi x (.5) squared. (Obviously, I haven't taken the time to figure out how to do math symbols in Blogger.) The volume of 10,000 coins would be 10,000 times that, which is about 1962.5 cubic inches.

The volume of a sphere is 4/3 x pi x (radius) cubed. So after plugging in the numbers and solving for the radius, we get 7.768 inches or a sphere about 15.5 inches in diameter, which happens to be about the size of the bag in the comic!

But the thousand pounds is obviously off. Doing some Googling, I found that AD&D2e changed the weight of coins so now 50 coins = 1 pound instead of 10 like before. That would make the bag in the comic weigh 200 pounds and, looking at historical weights of coins, that's pretty close to what they would weigh.

Hagar must be amazingly strong (as strong as Hercules?) to lift that 200 pound bag of 10,000 coins with one hand!

How do you handle the weight of coins in your game?