Winning percentage in Yahoo! Sports Fantasy Football is calculated as follows:

{Wins + 1/2(Number of Ties)} / Total Games Played

If a team plays a contest that results in a tie, it's counted as 1/2 win and 1/2 loss when determining their winning percentage.

For example, a team that finishes 7-6-1 will have a final winning percentage of .536, because [7 + .5(1)] / 14 = .536