Overview

The Bacon number is an informal measure of separation between a given performer and the American actor Kevin Bacon. It emerged from a parlor game called Six Degrees of Kevin Bacon, which applies the idea of "six degrees of separation" to movie credits: each shared appearance in a film creates a link. The Bacon number of an actor is the length of the shortest chain of co-appearances that connects them to Bacon.

How it is defined and calculated

Formally, consider a graph whose nodes are performers and whose edges join two performers who appear in the same movie. Kevin Bacon is the root node. His Bacon number is zero. Any performer who appears in a film with him has Bacon number 1. If a performer has not worked with Bacon directly but has worked with someone who has, their Bacon number is 2, and so on. The calculation seeks the shortest path between two nodes, typically found by breadth-first search or by consulting large film credit databases.

  • Kevin Bacon: Bacon number 0.
  • Direct co-star of Bacon: Bacon number 1.
  • Co-star of that co-star: Bacon number 2.

Origin and cultural impact

The game began as a campus-era joke in the 1990s and quickly entered popular culture. It highlights the small-world nature of the film industry and has been widely reported, parodied and adapted. Online tools and databases, notably industry credit indexes, have been used to compute Bacon numbers automatically. The concept also inspired related measures and playful rankings of centrality within entertainment networks.

The Bacon number is the entertainment equivalent of the Erdős number, which measures collaborative distance among mathematicians via co-authorship. People sometimes combine these to produce an "Erdős–Bacon number" for individuals with both academic papers and film credits. Beyond trivia, the Bacon number illustrates ideas from graph theory and network science such as shortest paths, connectivity components and small-world effects.

Computation, limits and notable points

Computing Bacon numbers in practice relies on accurate credit records. Major databases and scripts can produce shortest-path links; however, incomplete data or ambiguous credits may obscure connections. Some performers may lie in isolated components (no path to Bacon) if they work only in industries or productions not indexed. The Bacon number is a playful, not scientific, metric—but it remains a useful example when explaining networks, degrees of separation and the mathematical techniques used to analyze them.

Examples and variations

People use the Bacon number as a parlor trick, a classroom example and a gateway to broader network topics. Variations include restricting links to theatrical releases, TV appearances, or shared credits in specific genres. For further exploration and live queries, film credit resources and search tools provide interactive ways to trace chains of co-appearance and observe how central certain actors are within the cinematic collaboration graph.

See also: network centrality, small-world networks, and collaborative distance measures.