To calculate the potential payout of a winning handicap bet in horse racing, you start by identifying your stake and the odds provided for the horse you are betting on. You then compute your potential profit by multiplying your stake by the odds, which can be either in fractional or decimal format. After finding the profit, you add your original stake to this amount to determine the total payout. This total represents both the profit earned from the bet and the return of your initial wager.