How to read betting odds
Every sportsbook price says the same two things: how much you win if you are right, and how often you need to be right to break even. Three formats, one price.
By EdgeFast · Updated October 16, 2026 · Informational, not betting advice. 21+.
Three formats, one price
A sportsbook price can be written as American odds (−110), decimal odds (1.91) or fractional odds (10/11). All three describe the same payout. US books default to American odds, most of the world uses decimal, and UK racing still uses fractions. Once you can move between them, you can compare any two prices on the same footing.
American odds
American odds use a plus or minus sign and a number of 100 or more. A minus price is the favorite: −110 means you risk $110 to win $100 in profit. A plus price is the underdog: +150 means you risk $100 to win $150 in profit. In both cases you also get your stake back when the bet wins.
The number scales with your stake. At −110, a $55 bet wins $50. At +150, a $20 bet wins $30. The sign tells you which side of even money the price sits on, and the distance from 100 tells you how far.
Decimal odds
Decimal odds show the total return per $1 staked, stake included. At 1.91, a $100 bet returns $191: your $100 back plus $91 in profit. At 2.50, the same bet returns $250. Even money is 2.00. Anything below 2.00 is a favorite and anything above it is an underdog.
Decimal odds are the easiest format for arithmetic. Multiply the stake by the decimal price and you have the full payout. Multiply the decimal prices of parlay legs together and you have the parlay price.
Fractional odds
Fractional odds show profit over stake. 10/11 means $10 of profit for every $11 staked, which is the same price as −110 or 1.91. 3/2 means $3 of profit for every $2 staked, the same as +150 or 2.50. Odds of 1/1 are even money, often written as evens.
Implied probability
Implied probability turns a price into a break-even win rate. For a minus price, divide the number by the number plus 100: −110 is 110 ÷ 210, or 52.4%. For a plus price, divide 100 by the number plus 100: +150 is 100 ÷ 250, or 40%. For decimal odds, divide 1 by the price: 1 ÷ 1.91 is 52.4%.
That percentage is the share of bets you need to win just to break even at that price. It is not the true chance of the outcome. Both sides of a market add up to more than 100% because the book keeps a margin, which the vig guide explains. The implied probability calculator does the division for any price.
Why the format matters for a check
Two books can list the same bet at −110 and −105, or at 1.91 and 1.95. The difference looks small until you convert it: 52.4% against 51.2% is more than a point of break-even rate on every bet. A price check does this conversion for you across the listed books. When you compare prices by hand, convert both to one format first, usually implied probability. The better price is the one that asks for the lower break-even rate, and the +EV guide shows what that gap is worth.
Worked example
- Your ticket: Chiefs −3.5 at −110 for $100.
- Decimal: 100 ÷ 110 + 1 = 1.91. Fractional: 10/11. Implied probability: 110 ÷ 210 = 52.4%.
- Another book lists the same spread at +100. Decimal 2.00, fractional 1/1, implied probability 50%.
- On a $100 stake, −110 wins $90.91 and +100 wins $100.00. Same bet, $9.09 more if it wins, and a break-even rate 2.4 points lower.
Questions
Which odds format should I use?
Whichever you can read fastest. American odds match what US books show; decimal odds make the math easiest. The odds converter switches between all three and shows the implied probability for any price.
Why do both sides of a market add up to more than 100%?
The gap is the sportsbook margin, often called vig or hold. On a −110/−110 market each side implies 52.4%, so the two sides add to 104.8%. Read what vig is and how to remove it for the full picture.
Is a higher implied probability a safer bet?
No. Implied probability is the break-even rate the price demands, not the chance the outcome happens. A heavy favorite at −400 implies 80%, but that only tells you the book is pricing it as likely. Whether the bet is worth taking depends on the price you get compared with a fair one.
Does the format change my payout?
No. −110, 1.91 and 10/11 pay exactly the same. The format changes only how the price is written.