How to Read Betting Odds — American, Decimal & Fractional

American odds use a plus (+) or minus (-) sign relative to a $100 baseline. A minus number like -150 tells you how much you need to wager to win $100 in profit. So at -150, you would bet $150 to win $100, for a total return of $250. Minus odds indicate the favorite.

A plus number like +200 tells you how much profit you earn on a $100 wager. At +200, a $100 bet returns $200 in profit plus your original $100 stake, totaling $300. Plus odds indicate the underdog. The larger the plus number, the bigger the underdog and the higher the potential payout.

An even-money bet is expressed as +100 or -100 (also called EVEN or PK). At +100, you risk $100 to win $100. This represents a 50% implied probability before the vig is factored in. Most real bets will be listed at -110 on both sides, which builds in the sportsbook's margin.

Decimal odds are the easiest to calculate payouts with. Simply multiply your stake by the decimal number to get your total return (stake included). If the odds are 2.50 and you bet $100, your total return is $250 (which includes your $100 stake and $150 profit).

Converting from American to decimal is straightforward. For positive American odds: Decimal = (American / 100) + 1. So +200 becomes (200/100) + 1 = 3.00. For negative American odds: Decimal = (100 / absolute value of American) + 1. So -150 becomes (100/150) + 1 = 1.67.

Decimal odds of 2.00 represent an even-money bet. Anything below 2.00 is a favorite, and anything above 2.00 is an underdog. Many sharp bettors prefer decimal odds because they make it easy to spot value at a glance and quickly calculate parlay payouts by multiplying the decimals together.

Fractional odds, shown as 3/1 (read as 'three to one'), tell you the profit relative to your stake. At 3/1, you win $3 for every $1 wagered, plus your stake back. At 1/4, you win $1 for every $4 wagered. The first number is profit, the second is stake.

Fractional odds are most common in horse racing and UK sports betting. To convert fractional to decimal, divide the first number by the second and add 1. So 3/1 becomes (3/1) + 1 = 4.00 in decimal. And 1/4 becomes (1/4) + 1 = 1.25.

While less common in American sportsbooks, you will encounter fractional odds on some international platforms and in futures markets. Understanding them ensures you can compare value across any platform without getting confused by the format.

Every set of odds contains an implied probability, which is the sportsbook's estimated chance of that outcome happening (plus their margin). For American odds, calculate implied probability as follows: For minus odds, Implied % = |odds| / (|odds| + 100) * 100. At -150, that is 150 / 250 * 100 = 60%. For plus odds, Implied % = 100 / (odds + 100) * 100. At +200, that is 100 / 300 * 100 = 33.3%.

When you add the implied probabilities of all possible outcomes in a market, the total will exceed 100%. The amount above 100% is the overround, also called vig or juice. A typical NFL spread market might have -110 on both sides, giving implied probabilities of 52.4% + 52.4% = 104.8%. That extra 4.8% is the sportsbook's built-in profit margin.

Understanding implied probability is the foundation of finding value. If you believe a team has a 45% chance of winning, but the sportsbook is offering odds that imply only a 35% chance (+185), you have found a +EV bet. The gap between your estimated probability and the implied probability is where profit lives.

Line shopping means checking multiple sportsbooks to find the best available odds for the same bet. The difference between -110 and -105 on a spread bet might seem trivial, but over hundreds of bets it amounts to thousands of dollars in savings. Professional bettors consider line shopping non-negotiable.

To compare odds quickly, convert everything to decimal or implied probability. A moneyline of +155 at one book versus +165 at another is easily compared as decimal 2.55 versus 2.65 — the second book is clearly better. Use our odds converter tool to make instant comparisons without mental math.

Having accounts at 3-5 sportsbooks gives you access to the best available line most of the time. This is legal in every regulated state and is the single easiest way to improve your long-term results without changing anything about your handicapping process.