Take your top 20 artists. For each of these artists, collect the top 5 similar artists. The resulting number of unique artists is your eclectic score. If the score is small (extreme = 5) your musical preferences are very limited, and if it is large (extreme = 100), then you have an eclectic musical preference.
My eclectic score is currently
The 62 related artists for my profile are 3 Doors Down Acceptance AFI Angra Armor for Sleep (3) As Tall As Lions Ayreon Beyond Twilight Brand New Cartel (2) Casey Crescenzo Chiodos (3) Circa Survive (2) Circus Maximus Dashboard Confessional Disturbed Dream Theater Emanuel Emery (2) Fall Out Boy (5) Finch From First to Last Gatsby's American Dream Green Day Greg Howe Hawthorne Heights Hidden in Plain View Jason Becker KoЯn Limp Bizkit Linkin Park (2) Mae Marty Friedman My American Heart My Chemical Romance (3) Nickelback Opeth Panic! at the Disco (3) Papa Roach Planet X Porcupine Tree Portugal. The Man Saosin (2) Senses Fail (4) So They Say Symphony X (2) System of a Down Taking Back Sunday (8) The Academy Is... (2) The All-American Rejects (2) The Audition The Early November The Receiving End of Sirens (4) The Sound of Animals Fighting (2) The Starting Line The Used Thrice Thursday (2) Underoath (3) Vanden Plas Vinnie Moore Yellowcard (2)