Win percentage is calculated by the following formula:

( Wins * Ties / 2 ) / Games_Played

This formula is fairly standard, but hardly universal. For example Major League Baseball uses Games Behind, and the National Hockey League uses “Points Percentage” which is calculated as follows:

( 2 * Wins + Overtime_Losses ) / ( 2 * Games_Played )

To handle custom calculations, the mstw_ls_calc_percent filter is provided. After the calculation and before storing the result, it is passed to any registered callbacks. See the Actions & Filters man page for more information on this filter.