D20 Dice

The d20 is the most important and coveted die used in Dungeon & Dragons. It is an icosahedron, a polyhedron with 20 equilateral triangles, that is numbered 1 to 20. The numbers are arranged so that the largest number (20) is on the opposite side of the smallest number (1), the 2nd largest number (19) is on the opposite side of the 2nd smallest number (2), and so on. The sum of the opposite sides is always 21. Typically, a standard sized d20 measures 19mm to 20mm tall.

d20 dice are central to the core mechanics of many actions in Dungeons and Dragons: it determines if an attempt at something is successful such as attacks, saving throws, skill checks, and ability checks.