What is a d10?
A d10 is a ten-sided die used to generate one of ten outcomes. It is common in tabletop role-playing games both as a single die and as part of a two-die percentile roll.
Shape and geometry
Most modern gaming d10s use a pentagonal trapezohedron-style form with ten kite-shaped faces arranged around two pointed ends. Unlike the d4, d6, d8, d12, and d20 in their familiar regular forms, the common d10 is not one of the five Platonic solids.
Numbering conventions
A d10 may be marked 0–9 or 1–10. When a 0–9 d10 is used as a simple ten-outcome die, the rules may treat 0 as 10. In a percentile pair, one die usually represents the tens digit and the other the ones digit. A specially marked percentile die often shows 00, 10, 20, and so on.
Range and probability
For an ideal fair ten-outcome die, each marked outcome has probability 1/10, or 10%. If the die is interpreted as 1–10, the average result is 5.5. The meaning of a printed zero depends on the rules context and should not be inferred from the die alone.
D10s and percentile dice
Two d10s can generate values from 1 to 100 when one die is assigned to the tens digit and the other to the ones digit. The 00 and 0 combination is commonly interpreted as 100 in percentile systems. Because reading conventions can vary, the relevant game or rulebook should be treated as authoritative.
Common tabletop uses
D10s are used for ten-outcome tables, damage rolls, success-counting systems, percentage mechanics, random generation, and other game procedures. Some role-playing systems use large pools of d10s, while others use them mainly for percentile resolution.

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