Coinage
A standard [d20] coin weighs about a third of an ounce, so fifty coins weigh a pound.
| Coin | cp | sp | ep | gp | pp |
|---|---|---|---|---|---|
| Copper (cp) | 1 | 1⁄10 | 1⁄50 | 1⁄100 | 1⁄1000 |
| Silver (sp) | 10 | 1 | 1⁄5 | 1⁄10 | 1⁄100 |
| Electrum (ep) | 50 | 5 | 1 | 1⁄2 | 1⁄20 |
| Gold (gp) | 100 | 10 | 2 | 1 | 1⁄10 |
| Platinum (pp) | 1000 | 100 | 20 | 10 | 1 |
Background
Original D&D—“Basic” through Rules Cyclopedia—coins have an encumbrance of ∼ 1⁄10 pound each.
More specifically, encumbrance (enc.) is a combination of the weight and clumsiness of gear measured in coin-weight equivalents (cn), where 1 𝖼𝗇 equals approximately 1⁄10 of a pound in weight and awkwardness. For example, a 1⁄2 lb wineskin filled with a quart of water/wine (∼2 lb), would weigh ∼25 𝖼𝗇, but has an enc. of 30 𝖼𝗇.
Other units
A d20/D&D mile (𝗆𝗂𝖣) is 6,000 feet, and thus apparently a fantasy equivalent to the ≈6,076-foot nautical mile rather than the 5,280-foot land mile.
A nautical mile (𝖭𝗆𝗂) is one minute of latitude ( 1⁄60 1°), making Earth’s meridional circumference 21,600 𝖭𝗆𝗂. Since Earth is not a perfect sphere, the actual length of a minute of latitude varies between 1,813 𝗆 and 1,861 𝗆 with a de jure average of 1,852 𝗆 (≈6076.12-ft).
The original intent for the meter was to be one ten-millionth of 90° of latitude, making Earth’s m.circ. 40,000 ㎞. The best measurements at the time were slightly off and Earth’s actual m.circ. is ≈40,003 ㎞.
From this one can extrapolate that a standard D&D fantasy world could be:
- a 21,600 𝖭𝗆𝗂 ≈ 40,003 ㎞ m.circ. spheroid like Earth,
- a 21,600 𝗆𝗂𝖣 ≈ 39,502 ㎞ m.circ. spheroid with 2½% less surface area than Earth, or
- a 21,600 𝗆𝗂𝖣 = 40,000 ㎞ m.circ. sphere with D&D feet/inches etc. 1¼% longer than standard feet/inches.