d8

A d8, short for eight-sided die, is a polyhedral dice commonly used in tabletop role-playing games and board games. It is shaped as a regular octahedron, consisting of eight triangular faces that meet at six vertices. Each face carries a single integer from 1 to 8, and the die is designed to come to rest on one of its faces; the number on the upward-facing face is the result of the roll.

Materials and design vary. Most d8s are made from plastic or resin, though metal, wood, or gemstone variants exist. Sizes typically range from about 16 to 25 millimeters along an edge. The faces are labeled with numbers, often in high-contrast colors to improve readability. Some dice use different color schemes or font styles, but the numbering remains consistent across faces.

Use and notation. In gaming notation, 1d8 means roll one eight-sided die and use the resulting number. A roll of 2d8 sums the results of two independent d8 rolls. The probability distribution is uniform, with each outcome from 1 to 8 having a probability of 1/8. The expected value of a single d8 roll is 4.5.

Relation to other dice. The d8 is one of several standard RPG dice, alongside d4, d6, d10, d12, and d20. Its octahedral shape distinguishes it from dice with other geometries, affecting how it rolls and rests on a surface.