Sports Betting Odds Sports betting odds are what make the betting world turn. Different parts of the world express their odds differently as some use fractions, others use decimals and some times whole numbers. The betting odds determine how much money you will have to lay to win a certain amount. Depending on the odds, you might be laying more to win less, like when you bet the favorite. When you wager on the underdog, you will win more than lay on the game in the event of a win.