Decimal odds (European)
Decimal odds are the most widely used format in Europe and most countries worldwide. They are expressed as a decimal number (for example, 1.85, 2.50, or 4.00) and represent the total amount you receive for every euro staked, including the stake. To calculate your net profit, simply multiply your stake by the odds and subtract the initial stake. A €20 bet at odds of 3.00 returns €60 in total, meaning €40 in net profit.
The advantage of decimal odds is their simplicity: the higher the odds, the greater the potential payout, but also the more unlikely the event is considered by the bookmaker. Odds of 1.10 indicate a strong favorite with a very high implied probability, while odds of 10.00 suggest an outsider with only an estimated 10% chance of winning.
When comparing odds between different bookmakers, the decimal format makes reading much easier. A difference of 0.05 between two operators is immediately visible. Use our profit calculator to convert and compare odds quickly.
Fractional odds (British)
Fractional odds, also known as British odds, are the traditional format in the United Kingdom and Ireland. They are expressed as a fraction, for example 5/1 ("five to one") or 3/2 ("three to two"). The numerator indicates the potential profit and the denominator the required stake. Thus, odds of 5/1 mean you win €5 for every euro staked, plus the return of your stake. Odds of 3/2 return €3 for €2 staked.
To convert fractional odds to decimal odds, divide the numerator by the denominator and add 1. For example, 5/1 = (5÷1) + 1 = 6.00 in decimal. And 3/2 = (3÷2) + 1 = 2.50. Conversely, decimal odds of 2.25 correspond to 5/4 in fractional format. These conversions become second nature with practice.
Fractional odds are still common on British bookmaker sites, particularly for horse racing. If you bet with an operator that uses this format, most sites allow you to switch between formats in your account settings.
American odds (moneyline)
American odds, or moneyline, are the standard in the United States. They are expressed with a positive (+) or negative (-) sign. A positive line like +250 indicates the profit you earn from a $100 stake: here, $250 profit for $100 wagered ($350 total). A negative line like -150 indicates how much you need to stake to win $100: you must wager $150 to earn a $100 profit.
Negative odds denote the favorites and positive odds the underdogs. The larger the negative value (in absolute terms), the stronger the favorite. For example, -400 is a bigger favorite than -150. Conversely, +500 is a bigger underdog than +200.
To convert to decimal odds: if the line is positive, divide by 100 and add 1 (+250 = 3.50). If negative, divide 100 by the absolute value and add 1 (-150 = 1.667). With the growth of the American sports betting market, this format is becoming increasingly common internationally.
Calculating implied probabilities
Every set of odds reflects an implied probability — the bookmaker's estimate of the chance that a result will occur. For decimal odds, the implied probability is calculated simply: 1 divided by the odds, multiplied by 100. Odds of 2.00 imply a 50% probability, odds of 4.00 imply 25%, and odds of 1.50 imply 66.7%.
The sum of implied probabilities for all outcomes always exceeds 100%. This excess, called the overround or margin, constitutes the bookmaker's mathematical edge. For example, in a tennis match with odds of 1.80 and 2.10, the implied probabilities are 55.6% and 47.6%, totaling 103.2%. The margin is therefore 3.2%. The lower the margin, the more favorable the odds are for the bettor.
Knowing how to calculate implied probabilities is fundamental for identifying value bets. If your own estimate of the probability of an outcome is higher than the implied probability of the odds, the bet represents positive expected value in the long run. This is the very principle that guides professional bettors. Check out our beginner's guide to put this knowledge into practice.