What American odds actually tell you
American odds (also called moneyline odds) are the plus/minus prices you see at every US sportsbook: +150, -110, -350. The sign and the number together describe two things at once: which side is favored, and how much you win or risk per $100. Once you can read them fluently, you can do the one calculation that matters most in betting: turning a price into a probability. That probability is the foundation for everything else, from spotting a good number to understanding why the house keeps an edge.
The rule is simple. A negative number is the favorite and tells you how much you must risk to win $100. A positive number is the underdog and tells you how much you win on a $100 risk. The $100 is just a unit for reading the price, not a required bet size.
Reading the two formats with payout math
Negative odds (favorites), e.g. -110. You risk $110 to win $100. Your profit if it hits is $100, and you get your $110 stake back too, for a $210 total return. The general formula for profit on a negative price is:
- Profit = Stake × (100 / |odds|)
So a $55 bet at -110 returns 55 × (100/110) = $50 profit. A $100 bet at -350 returns 100 × (100/350) = $28.57 profit. The bigger the negative number, the heavier the favorite and the smaller the payout.
Positive odds (underdogs), e.g. +150. You win $150 on a $100 stake. The formula for profit is:
- Profit = Stake × (odds / 100)
A $40 bet at +150 returns 40 × (150/100) = $60 profit, plus your $40 back, for $100 total. A +250 underdog pays $250 profit per $100 risked. The bigger the positive number, the longer the odds and the larger the payout.
A quick sanity anchor: +100 and -100 are the same price, an even-money bet. Risk $100 to win $100. Anything more negative than -100 is a favorite; anything more positive than +100 is a dog.
Converting American odds to implied probability
Every price contains a break-even probability, the win rate you would need just to not lose money over time. This is the number professionals actually care about. There are two formulas, one for each sign.
Favorites (negative odds):
- Implied probability = |odds| / (|odds| + 100)
For -110: 110 / (110 + 100) = 110 / 210 = 52.4%. So a -110 bet needs to win about 52.4% of the time to break even. For -350: 350 / 450 = 77.8%.
Underdogs (positive odds):
- Implied probability = 100 / (odds + 100)
For +150: 100 / (150 + 100) = 100 / 250 = 40%. A +150 underdog must win 40% of the time to break even. For +250: 100 / 350 = 28.6%.
Reading it back the other way is just as useful: if your own read says a team wins 45% of the time, you need a price that implies 45% or less to have an edge. +150 implies 40%, so at +150 you would have value on a team you think is a genuine 45% shot.
Why the implied number is inflated: the vig
Here is the catch that trips up new bettors. Add up the implied probabilities on both sides of a market and they do not sum to 100%. They sum to more than 100%. That surplus is the sportsbook's built-in margin, known as the vig, juice, or hold.
Take a classic -110 / -110 market, two sides of a point spread:
- -110 implies 52.4%
- -110 implies 52.4%
- Total = 104.8%
That extra 4.8% is the overround. It means the price you see is not the book's honest estimate of the outcome, it is that estimate padded with margin. To find the fair, no-vig probability, you normalize each side by the total:
- Fair probability = 52.4% / 104.8% = 50.0%
So a -110/-110 market is really a 50/50 coin flip that the book is charging you a toll to bet on. This normalization step is called de-vigging, and it is how you recover a fair price from a public line. On a lopsided market like -350 / +280, the two raw probabilities (77.8% and 26.3%) sum to about 104.1%; dividing each by that total gives the de-vigged fair prices you should actually compare your model against.
This is exactly why a bet that wins slightly more than half the time can still lose money at -110, and why shopping for the best number across books matters so much. A team priced -110 at one book and +100 at another is a real difference in your break-even rate (52.4% versus 50.0%) for the identical wager.
Turning the math into an edge
Once you can de-vig a market, you can measure expected value (EV): compare your estimated win probability to the price's break-even probability. If a de-vigged market says a side is truly 55% and a different book still offers it at -110 (52.4% break-even), that gap is a positive-EV bet. Over the long run you can also track closing-line value (CLV), whether you consistently beat the price the market settled at, which is one of the more reliable signals that your process is sound rather than just lucky.
Doing this by hand across 40+ books and thousands of markets is not realistic. That is what today's edges on EdgeFinder automates: it pulls live odds across MLB, NBA, NFL, NHL, college, and soccer, de-vigs each market to a fair price, and surfaces the spots where a book's number is out of line with the fair estimate. A self-training model (finals-updated Elo, Pythagorean expectation, starting-pitcher and situational terms, anchored to the market) is graded against a public, verifiable log of pregame predictions, so you can judge the method rather than take a claim on faith. The free tier shows top picks; signing up unlocks full coverage for $9.99/mo.
None of this makes any single bet a sure thing. Odds describe probabilities, not certainties, and even a well-priced +EV bet loses plenty of the time. This is education, not a promise of profit. Bet only what you can afford to lose, 21+, and check the rules in your jurisdiction.