 5 rounds , etc . In this case , for n players / teams where n is not a power of 2 , log2 n is rounded up since it is necessary to have at least one round in which not all remaining competitors play . For example , log2 6 is approximately 2 @.@ 585 , which rounds up to 3 , indicating that a tournament of 6 teams requires 3 rounds ( either two teams sit out the first round , or one team sits out the second round ) . The same number of rounds is also necessary to determine a clear winner in a Swiss @-@ system tournament . 
