A color photo of a red twenty-sided dieDice are used in games around the world to generate a random number. Traditionally the die is cubical; however there are multiple forms of non-cubicle die, such as, the 20-sided die. Ancient die were typically made from bones, wood, or rock. Today, die of all shapes are usually made from resin.

The 20-sided die can be traced back to the Romans, however this ancient tool for generating numbers was put to a new purpose in 1974 in Lake Geneva, Wisconsin. In 1974 Gary Gygax incorporated the 20-sided die into a new game he had invented. That game was called Dungeons & Dragons.

A color photograph showing six types of die in various colors
Die come in many shapes, but they do not all generate numbers with the same likelihood. Image courtesy of Kate Wersan.

Before adopting the die, Gygax’s now-famous game asked players to randomly draw numbered poker chips from a bag. This method was cumbersome, limited the game’s portability, and was not sufficiently random. Gygax adopted the new die because the shape of the 20-sided die offers an equal five percent probability for each outcome. The more commonly used six-sided cubical dice do not offer equal probability and are relatively predictable in their results. With two six-sided die, for instance, rolling a 6, 7, or an 8 is frequent, while 2’s and 12’s are rare. This does not create equal probability in a combat with monsters!

A picture of the 1974 rulebook for the roleplaying game, Dungeons and Dragons
The rulebook from 1974 for the roleplaying game, Dungeons and Dragons. Image via Flickr.

In his fantasy-based tabletop game, Gygax introduced Americans to a new kind of role-playing game where all players needed was the rule book, seven types of dice, pencil, paper, a sheet of graph paper, and their imagination. Players create their own personas, endowed with characteristics achieved by a roll of a die. Once the brave companions have started their adventure, the 20- sided die became the most important die used in the game. That die controls the strategies and attacks made by players; an ancient tool put to new uses!

Written by Mallory Zink, June 2018.


Duke, Galen. Dungeons & Dragons: 40 Years of a Wisconsin Invention, Wisconsin Public Radio, 20 Jan. 2014, https://www.wpr.org/dungeons-dragons-40-years-wisconsin-invention. Accessed 21 Dec. 2017.

Dungeons & Dragons; New to the Game, What is D & D?, Wizards of the Coast LLC, dnd.wizards.com/dungeons-and-dragons/what-is-dd. Accessed 21 Dec. 2017.

Kusher, David. Dungeon Master: The Life and Legacy of Gary Gygax, Wired, 10 Mar. 2008, https://www.wired.com/2008/03/dungeon-master-life-legacy-gary-gygax/. Accessed 21 Dec. 2017.

Metropolitan Museum of Art, metropolitan Museum of Art,https://www.metmuseum.org/art/collection/search/551072. Accessed 21 Dec. 2017.

Morrisy, Anne. Dungeons & Dragons: A Journey of Imaginations, At the Lake, Geneva Lakes Area Magazine, 25 Nov. 2014, atthelakemagazine.com/dungeons-dragons/. Accessed 21 Dec. 2017.

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