Enquiring DMs want to know: how big are the gold coins being looted in their Dungeons & Dragons 5e campaign? We've crunched the numbers to find the answer.
According to the 5e Player's Handbook, fifty coins weigh a pound. That means a single coin weighs 0.02 pounds, or 9.1 grams. But what are their size?
Fine (99.95% pure) gold has a density of 19.3 grams per cubic centimetre. With 9.1 grams of gold, we can make a coin with a volume of 0.47 cm³.
Now that we have a fixed volume, we can decide the coin's thickness to find its diameter using the formula for the volume of a cylinder (V = π × r² × h). A D&D coin with a thickness of 1.5mm would have a diameter of 20mm.
Our Classic Fantasy coins are a bit thicker at 2mm to feel better in your hand. At 19mm across our 1-Gold coins are pretty much bang-on the measurements of a coin you'd find in a Forgotten Realms chest, assuming the chest is not a mimic. (We jest. It’s always a mimic.)
Of course, our zinc-based alloy is lighter than real gold to save you on shipping! The 1-Gold coins weigh about 3.5 grams each (which happens to be the weight of most guilders and florins, the dominant gold coins of Europe in the late Middle Ages and Renaissance.)