Underdog
What does "underdog" mean in sports betting?
The underdog is the side the market expects to lose. On a moneyline it usually has a plus number, and on a spread it gets points.
A plus number shows how much profit a $100 bet wins. The bigger the number, the less likely the market thinks that side is to win.
Underdogs lose more often than they win, but that alone doesn't make them bad bets. The question is the same as with any price: does this side win more often than its implied probability says?
Example
Team B is +180. A $100 bet wins $180 profit, and the price implies 35.71%, which is your breakeven. If you think Team B wins 40% of the time, EV is 0.40 x $180 - 0.60 x $100 = +$12 per $100 bet. If you think it's 35%, EV is 0.35 x $180 - 0.65 x $100 = -$2.
Related terms
Moneyline
A moneyline bet is a wager on which team or fighter wins outright, with no point spread involved.
Point spread
The point spread is a handicap that evens out a matchup: the favorite has to win by more than the spread, and the underdog covers by losing by less than it or winning outright.
Implied probability
Implied probability is the win chance a price suggests. It turns odds into a percentage so you can compare them with your own estimate.
American odds
American odds show how much you risk to win $100 (minus numbers) or how much you win on a $100 bet (plus numbers).
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