What is a d12?
A d12 is a twelve-sided die that normally produces results from 1 through 12. It is one of the familiar polyhedral dice included in many tabletop role-playing game sets.
Shape and geometry
The standard d12 is usually based on a regular dodecahedron, one of the five Platonic solids. It has twelve pentagonal faces, twenty vertices, and thirty edges. Its relatively large faces make numerals easy to display even on compact dice.
How a d12 is read
The d12 rests on one face after a roll, and the upward-facing numeral is normally used as the result. Number placement, opposite-face relationships, typeface, orientation, and engraving vary by manufacturer and should be documented from the individual product rather than assumed.
Range and probability
A conventional d12 has twelve equally defined outcomes numbered 1 through 12. In an ideal fair model, each result has probability 1/12, about 8.33%. The average result is 6.5.
Common tabletop uses
D12s are often used when a game needs a relatively broad single-die range. Examples include damage values, hit points, random tables, encounter generation, calendar or month-like randomization, and specialized mechanics. These functions are defined by individual games and are not inherent properties of the die.
Variants and materials
Most d12s use Arabic numerals, but twelve-sided symbol dice also exist. The same basic geometry can be produced in resin, plastic, metal, wood, stone, and other materials, with rounded or sharper edge treatments. A twelve-sided product may also use different numbering ranges or repeated symbols, so “d12” should describe the outcome structure or face count in context.

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