• Kevin Bacon has a Bacon number of zero.
• The Bacon number of actor or actress A is defined to be the minimum of the Bacon numbers of all the actors or actresses with whom A appeared in a movie produced by a major studio, plus one. The most common source used to determine whether or not a film is valid is whether or not it is present on the Internet Movie Database.

However, the majority of actors do have a Bacon number of 2 or 3. The higher the Bacon number of an actor, the less connected they are to other actors. Using one of the actors with the highest known finite Bacon number (8), William Rufus Shafter as the centre of the acting universe instead of Bacon, we can find two actors with a Rufus Shafter number of 15.

The Bacon number is an application of the same idea as the Erdös number in Mathematics to the movie industry. Remarkably, Paul Erdös himself has a Bacon number of 4, due to his appearance as himself in the 1993 film N Is a Number.

Notably, Bacon is not the most linkable actor. That honour (as at July 15, 2003) goes to Rod Steiger, with an average Steiger number of 2.660. By contrast, the average Bacon number is 2.943.

But note: according to the Oracle of Bacon at Virginia,

"About 12% of all actors cannot be linked to the rest of the movie universe, either because they have appeared only in TV features or straight-to-video releases that the Oracle doesn't count, or because they have not appeared in any features with actors from the Hollywood mainstream."