American Odds Explained: Favorites, Underdogs, and Payouts
American odds, also called moneyline odds, are the standard format used by North American sportsbooks. At first glance, a string of large positive and negative numbers can look confusing. This guide demystifies them completely: what the sign means, how the payout math works, and how to quickly translate any American odds number into the probability it implies.
The Sign Is Everything
The single most important piece of an American odds number is its sign: positive or negative. It immediately tells you whether you are looking at a favorite or an underdog, and it determines which formula you use to calculate the payout.
- Negative (−) = Favorite. This team is expected to win. You must stake more than $100 to profit $100.
- Positive (+) = Underdog. This team is expected to lose. A $100 stake returns more than $100 in profit if successful.
In rare cases, both sides of a game may carry negative odds, or one side may sit close to -100 / +100. This happens when the market views the game as very close to a coin flip, but one side is still marginally favored.
Negative Odds: The Favorite
Reading a negative number is straightforward once you establish the anchor: the question being answered is always “how much do I stake to profit exactly $100?”
Examples with Negative Odds
The payout formula for negative odds is:
So if you stake $50 on a -150 favorite: profit = (100 / 150) × 50 = $33.33. Your total return is $83.33 (stake back plus profit).
Positive Odds: The Underdog
Positive numbers answer a different question: “if I stake exactly $100, how much profit do I win?” The larger the number, the bigger the underdog, and the bigger the potential payoff.
Examples with Positive Odds
The payout formula for positive odds is:
So if you stake $50 on a +200 underdog: profit = (200 / 100) × 50 = $100. Your total return is $150.
Calculating Implied Probability
Every set of American odds encodes an implied probability, the market's best estimate (including the house margin) of how likely that outcome is. There is a different formula for each sign:
A -180 favorite implies 180 / 280 = 64.3%. A +150 underdog implies 100 / 250 = 40.0%. When you add both sides, you get 104.3%, the excess above 100% is the vig. For a deep dive into this math and how to remove the vig to find fair probabilities, see our guide on converting odds to probability.
-110 and the Standard Vig Line
You will see -110 more than any other number in American sports markets. It is the default price applied to both sides of a spread or totals bet when the market believes each side is close to equally likely after the handicap is applied. The -110 / -110 structure creates the standard vig, requiring bettors to win 52.4% of their selections just to break even.
When lines move off this standard, say, one side goes to -115 while the other moves to -105, it signals that money is flowing disproportionately to one side, and the book is rebalancing its exposure. Tracking these movements on live market lines, as OwnTheLines does, gives you a real-time view of where money is being concentrated.
Common Misconceptions
“A big underdog is always worth picking.”
High positive odds are appealing, a +400 underdog returning $400 on $100 is exciting, but the market implies only a 20% chance of winning. That means you should expect this team to lose 4 out of 5 times. Over a large sample, you need to find underdog prices that are higher than truly warranted to show a profit.
“Betting the favorite is always safer.”
Favorites win more often, but heavy favorites pay very little. A -400 favorite wins frequently but returns only $25 profit per $100 risked. If that team loses even once in five games, you barely break even. The safety narrative ignores the return-to-risk math that underpins long-run performance.
“Recent wins predict future prices.”
Markets are forward-looking and adjust quickly for roster news, travel fatigue, match-up data, and historical patterns. A team on a five-game winning streak may not carry a favorable price if analysts expect a regression. Odds represent the collective wisdom of thousands of sharp bettors, not just last week's score.
Using American Odds in Fantasy Competitions
On OwnTheLines, all selections reference live market American odds. You choose from moneyline, spread, or totals markets, the same structures real markets use, and selections are graded against actual game outcomes. Because no money is wagered, the only thing on the line is your analytical credibility within your league.
Understanding how to read the numbers means you can approach each selection as a calibrated probability decision, not a gut feel. Over the course of a full season, the gap between calibrated decision-making and intuition becomes very visible in the standings.
Learn about the broader context of how odds are set in our how sports odds work guide.
Frequently Asked Questions
What do negative American odds mean?
Negative American odds (e.g., -150) indicate a favorite. The number shows how much you must stake to win $100 in profit. -150 means you risk $150 to net $100.
What do positive American odds mean?
Positive American odds (e.g., +200) indicate an underdog. The number shows how much profit a $100 stake would return. +200 means a $100 bet profits $200.
How do I calculate implied probability from American odds?
For negative odds: implied probability = |odds| / (|odds| + 100). For example, -150 gives 150/250 = 60%. For positive odds: implied probability = 100 / (odds + 100). For example, +200 gives 100/300 = 33.3%.
What does -110 mean and why is it so common?
-110 is the standard vig applied to most sides and totals bets. It means you risk $110 to win $100. The extra $10 is the bookmaker's margin. It makes the break-even win rate approximately 52.4% rather than 50%.
Can American odds be +100 or -100?
+100 odds represent a true even-money bet: a $100 stake wins $100 profit, implying a 50% probability with no vig. -100 is the same thing expressed from the other direction. Both are functionally even money, meaning the bookmaker claims no edge.