What Is an Underdog in Sports Betting?

In basic sports betting theory, the underdog is any team or player that is commonly expected to lose a given two-way contest. 

Here’s an easy example. In the 2023 college basketball national championship, four-time champion UConn played San Diego State. The underdog was San Diego State. The Aztecs were expected to lose, and they did.

For readers who want a more technical and nuanced answer, consider that sports betting terms like favorite and underdog are less about which team “should win” and more about providing roughly equal betting incentives to both sides of a market. 

Let’s return to my national championship example. A majority of bettors are going to want to back UConn to beat San Diego State. That majority appetite to bet one side over another creates an uneven distribution of action.

To even out this difference, online sportsbooks create additional incentives to bet on the underdog. 

In a moneyline market, an underdog like San Diego State pays out at a greater rate than a favorite. 

In a point spread market, an underdog like San Diego State will be given the additional advantage of a point spread to cover. If the underdog’s final score differential falls inside the point spread margin, the underdog will be the winning side, even if they didn’t necessarily win the game.

How To Know What Team Is the Underdog in Sports Betting

As a general rule, bettors can identify the underdog in American betting markets by looking for the plus sign (+). 

In moneyline markets, underdog prices are represented by a plus sign and a large number. At BetMGM, San Diego State opened the aforementioned national championship game as a +220 moneyline underdog, meaning a successful $100 bet would have returned $100 of principal plus an additional $220 of winnings.

In spread markets, bettors can identify the underdog by looking for the point spread with the plus sign. At BetMGM, San Diego State opened as a 6.5-point underdog, so they would have appeared as +6.5 in the sportsbook.

In rare cases, neither team is favored to win, so there is no favorite or underdog. Both sides have roughly even payouts. This kind of contest is typically referred to as a pick ‘em.

In some sports like soccer, bettors may be wagering in a three-way market, which may provide more than one side priced with a plus sign.