The d12, properly introduced
Plato assigned four of the five perfect solids to the elements and reserved the dodecahedron for the cosmos itself, writing in the Timaeus that the god used it "for embroidering the constellations on the whole heaven." Roman dodecahedral objects survive by the hundreds, though nobody agrees what they were for. As a die it is the underdog of the RPG set, prized by players precisely because so few rolls call for it.
Roll it for: great-axe damage and other heavy hits in d&d; random months or hours; twelve-way choices, one per zodiac sign if you like. And if the d12 isn't the die your game asks for, the full dice roller has the other five.
- 12, numbered 1 to 12
- Dodecahedron, a Platonic solid
- 8.3% — exactly 1 in 12
- 6.5
- averages 13; totals range 2 to 24
- two 12s in a row: 1 in 144
D12 — frequently asked
A 12-sided die shaped as a dodecahedron, one of the five Platonic solids. Twelve pentagons; the Greeks thought it mapped the heavens. Faces are numbered 1 to 12, and on a fair d12 each lands with exactly a 8.3% chance.
One in 12, or 8.3%, the same as every other face. Rolling two 12s back to back happens once in 144 attempts. The roller here uses rejection sampling on a cryptographic generator, so those odds hold exactly.
6.5. A fair die averages the midpoint of its range, so 2×d12 averages 13 and 3×d12 averages 19.5. Single rolls are flat: an average result is no more likely than a 12 or a 1.
Great-axe damage and other heavy hits in D&D; Random months or hours; Twelve-way choices, one per zodiac sign if you like. Beyond those, any decision with 12 options maps onto it directly.