Basically you divide the total number of fans of your top 10 artists by the total number of fans of the top 10 of last.fm as a whole.
Mine
65daysofstatic : 14,973
Coheed and Cambria : 97,641
Queens of the Stone Age : 164,469
Oceansize : 12,268
Mogwai: (I'll ignore them cos I'm not even a fan and don't own any of their albums or have even listened to one!)
Bloc Party : 173,961
Biffy Clyro : 17,410
Test Icicles : 20,039
New Found Glory : 73,276
Hundred Reasons : 12,568
Yourcodenameis:milo : 4,476
Total : 591,081
Last.fm's
Red Hot…