What is a d8?
A d8 is an eight-sided die used to produce one of eight results, normally numbered 1 through 8. It is a standard member of the polyhedral dice set commonly used in tabletop role-playing games.
Shape and geometry
The familiar d8 is usually a regular octahedron. It has eight triangular faces, six vertices, and twelve edges. Its shape can be visualized as two square-based pyramids joined at their bases.
How a d8 is read
Because an octahedral d8 rests on one face, the numeral on the uppermost face is normally read as the result. Products may vary in font, engraving depth, orientation, color, and opposite-face layout, so the markings should be treated as part of the product specification rather than assumed from the geometry alone.
Range and probability
A conventional d8 produces the integers 1 through 8. For an ideal fair d8, the probability of any specific result is 1/8, or 12.5%. The average result is 4.5. As with all dice, theoretical equal probability describes the mathematical model; it does not independently verify the fairness of a particular manufactured die.
Common tabletop uses
D8s commonly appear in damage rolls, healing rolls, hit-point systems, encounter tables, resource generation, and other mechanics that need a range larger than a d6 but smaller than a d10. These examples are typical uses rather than universal rules.
Numbering and variants
Most tabletop d8s use Arabic numerals, but symbol dice and custom-marked eight-sided dice also exist. Materials range from injection-molded plastic and resin to metal, wood, stone, and specialty composites. Edge treatment and size can change handling without changing the basic eight-outcome notation.
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