Betting odds tell you two things at once: how much a bet pays, and what chance the book is giving the outcome. A price of -150 means you stake $150 to win $100 and implies a 60% chance; +200 means $100 wins $200 and implies 33.3%.
The same price can be written three ways, American, decimal and fractional, and every one of them converts to a percentage. This guide shows how to read each format, how to turn a price into a probability, and how to see the book’s margin inside a line.
How to read American odds
American odds, also called moneyline odds, are the standard format at US sportsbooks. A minus number is the favorite and shows what you stake to win $100. A plus number is the underdog and shows what $100 wins.
- -150: stake $150 to win $100, for $250 back in total
- +200: stake $100 to win $200, for $300 back in total
- -110: stake $110 to win $100, the usual price on a point spread or total
You do not have to bet in hundreds. At -150, a $30 bet wins $20; at +200, a $30 bet wins $60. Our guide to what a moneyline is goes further.
Decimal and fractional odds
Decimal odds show the total return on a $1 stake, stake included. At 2.50, $10 returns $25: $15 of profit and your $10 back. To convert from American, a plus price becomes 1 + price/100, so +200 is 3.00, and a minus price becomes 1 + 100/price, so -150 is 1.67.
Fractional odds show profit against stake. At 5/1, every $1 staked wins $5, so a $2 bet wins $10 and returns $12. At 3/2, $2 wins $3. You will still see fractions on horse racing and in UK markets; 1/1 is even money, the same as +100 or 2.00.
Turning a price into a probability
Every price implies a chance, and the arithmetic is short.
| Format | Formula | Example | Implied chance |
|---|---|---|---|
| American, plus | 100 / (price + 100) | +125 | 44.4% |
| American, minus | price / (price + 100) | -150 | 60.0% |
| Decimal | 1 / price | 2.50 | 40.0% |
| Fractional a/b | b / (a + b) | 5/1 | 16.7% |
That percentage is the book’s price, not the truth. A bet is worth making only when your own estimate of the chance is higher than the implied one. At -110, you need to win 52.4% of the time just to break even.
The book’s margin, and how to find it
Add up the implied chances of every outcome in a market. On a fair coin priced honestly, the two sides would total 100%. At a sportsbook they total more, and the excess is the margin, also called the vig or juice.
At -110 on both sides of a spread, each side implies 52.4%, for 104.8% in total. The book is charging 4.8 points over fair, and if it takes equal money on both sides it keeps 4.5% of everything wagered, because it pays $210 back on every $220 it collects. In Super Bowl LX, Seattle closed at -230 and New England at +190: 69.7% plus 34.5%, or 104.2%.
To strip the margin out, divide each side’s implied chance by the total. At -230 and +190, Seattle’s no-vig chance is 69.7 / 104.2, or 66.9%, and New England’s is 33.1%. Those are the numbers to compare with your own.
Using implied probability
Shop the price. The same side at -105 instead of -110 lowers your break-even rate from 52.4% to 51.2%, and over hundreds of bets that gap decides whether a bettor who picks 52% winners makes money. The same check works on props; our props guide and prop betting guide cover those markets.
Futures boards show the same thing. Add up every team’s implied chance on a title market and the total comes to more than 100%, because each price carries the margin. A team at +1000 is priced at 9.1%, and that is the number your own estimate has to beat.
Hedging, middling and arbitrage
These three use the same arithmetic on two or more bets.
A hedge is a second bet against your first, placed later at a new price, to lock in part of a result. It lowers risk and costs upside. Our hedge bet guide works through examples.
A middle takes both sides of a line that has moved. If you took a team +3.5 and the line later moves so you can take the other side -2.5, a win by exactly 3 wins both bets; any other result wins one and loses one, so you pay the margin once. Our guide to alternate total points covers the lines that make this possible.
An arbitrage bets every outcome at different books when their prices add up to less than 100%. With +110 at one book (47.6%) and -105 at another (51.2%), the total is 98.8%. Staking $48.18 and $51.82 returns about $101.17 whichever side wins. The edge is small, and books may limit accounts that do it often.
Prices move fastest during games; our guide to live betting covers that market. If you would rather follow a handicapper, see our buy picks page, check the SportsHub leaderboard, or sign up with SportsHub.