Divide the first number of the odds by the second number to convert the odds to decimal format. As an example, 11-2 odds would convert to 5.5.
Add one to this figure, since you will be receiving your original bet back as well. In the example, the number becomes 6.5.
Multiply this number by your original bet to calculate total winnings. In the example, if you had bet $200, you would receive $1,300.
Subtract your original bet to calculate the actual amount gained. In the example, you would have walked home with $1,100 more money than when you started.