Every set of odds tells you two things: what you get paid if you win, and what chance the book is assigning to that outcome. If you cannot read a price quickly, you cannot tell whether a bet is worth taking. The format itself is just arithmetic. The implied probability behind it is the part that makes or loses you money.
American Odds and the -110 Standard
American odds are a positive or negative number, and every US-facing book, offshore or domestic, uses them by default.
A negative number is what you risk to win $100. At -110 you put up $110 to win $100. At -200 you put up $200 to win $100. At -350 you put up $350. The bigger the negative number, the heavier the favorite.
A positive number is what you win on $100. At +110 you win $110 and get back $210. At +200 you win $200 and get back $300. At +450 you win $450 and get back $550. A positive price means an underdog.
Point spreads and totals are priced at -110 on both sides almost everywhere. The book is saying both teams are equally likely to cover, and it is charging you $10 per $100 for the privilege of betting. That $10 is the vig, and it is the whole reason the book stays in business.
Decimal Odds Are the Easiest to Compute
Decimal odds show your total return per unit staked, with your stake included. Multiply the odds by your bet and you have the amount coming back.
2.00 is even money: bet $100, get back $200, profit $100. 1.91 is the same as -110: bet $100, get back $191, profit $91. 3.50 is the same as +250: bet $100, get back $350, profit $250. Anything under 2.00 is a favorite.
Decimal is the standard in Europe, Australia and most of the world. If you bet soccer or tennis at a book like Everygame, which is built for international sports, you will see decimal prices often, and most books let you switch the display in your account settings.
Fractional Odds and Where You Still See Them
Fractional odds show profit relative to stake. They survive mainly in UK horse racing and traditional British bookmaking.
5/1 means you win $5 for every $1 you bet, so $100 returns $600. 2/1 wins $2 per $1, so $100 returns $300. 1/2 wins $1 for every $2 you bet, so $100 returns $150. Anything under 1/1 is a favorite. The -110 standard is 10/11 in fractional terms, which is why you rarely see a spread quoted that way.
Converting Between the Three
You do not need a calculator, but it helps to know the shape of the math.
- Negative American to decimal: 100 divided by the number, plus 1. -200 becomes 1.50.
- Positive American to decimal: the number divided by 100, plus 1. +250 becomes 3.50.
- Decimal to fractional: subtract 1 and write it as a fraction. 3.50 becomes 5/2.
So -110, 1.91 and 10/11 are the same price. +150, 2.50 and 3/2 are the same price. The book is not giving you a better deal in one format. It is the same number in a different costume.
Implied Probability Is the Number That Matters
Every price implies a win probability, and this is the part most new bettors skip. For a negative number, divide the number by the number plus 100. For a positive number, divide 100 by the number plus 100.
-110 implies 52.4%. -200 implies 66.7%. +150 implies 40%. +250 implies 28.6%.
Here is why that matters. If a team is +150 and you believe it wins half the time, you are getting paid as if it wins 40% of the time. That is a good bet. If you believe it wins 35% of the time, the same +150 is a bad bet. Sports betting, stripped of everything else, is the job of finding prices where the implied probability is lower than the real one. You cannot do that job if you do not know what the price implies.
Vig, and Why -105 Beats -110
Add up the implied probabilities on both sides of a standard -110/-110 line and you get 104.8%, not 100%. That extra 4.8 points is the book’s margin, and it works out to about 4.5 cents on every dollar wagered. On a coin flip you have to win 52.4% of the time just to break even.
A reduced-juice line at -105/-105 adds up to 102.4%, and your break-even drops to 51.2%. Over a season of a few hundred bets, that 1.2 point difference is real money. SportsBetting.ag posts a standing -105 on NFL and NBA sides, which is the main reason it belongs in your rotation even though the interface looks dated.
Where to Bet Once You Can Read the Board
Learn the implied probability of -110, +100, -150 and +150 by heart and you will read any board in seconds. Then go find the better price. Our sportsbook reviews cover which offshore books post -105, which post early lines, and which pay out fastest, so you can open accounts where the math is already on your side.