When you start in the world of online sports betting, the first question which appears is “what are the odds?” Basically an odd is a probability. The number that appears to designate this probability, also indicate what value you you can win by betting on a particular event or outcome. In traditional gambling houses, as **Dhoze** for example, the odds are established by its professionals, so that represent the probability of a given event happen. The odds are calculated with statistical data, information on the teams, and a number of other important data about the games or events that will take place.

In a betting exchange, as **Betfair**, odds work in a different way. As Betfair is a betting exchange, the values of probabilities are defined depending on the volume of bets placed between the various players. It is the very community of bettors who directly or indirectly defines the value of the probability for that event or result.

As a rule, the value of an odd (probability) is inversely proportional to the estimated probability of victory. This means that if we bet in favor of a team that has a low odd, we have a greater chance of victory. The same is true if we invest in a team that has too high odds, in the probability of winning is very low as well.

**Different types of odds (Probability)**

Typically, a traditional bookmaker, offers three different types of odds, based on different international betting markets: The Odds Decimal Style, Odds Fractional Style, and in the Odds in American style. To understand more easily how these different types of odds, we analyze in detail each of them.

**Odd Decimal or European**

The Decimal Odd is the most common in sports bookmakers, as a Odd European origin. It is normally one odd in whole or decimal format. To calculate a decimal Odd, divide 1 by the probability of victory. If when entering a bookmaker are available several odds for games and events and you want to determine how much you win by betting on that outcome, the formula to calculate will be:

*Probability = 1 / odd. To calculate the profit (W), you must use the following formula: W = amount wagered * (odd – 1).*

To understand more easily how it works the Odd Decimal, let’s look at an example of a game of the Champions League between Arsenal and AC Milan:

– The odds for Arsenal’s victory is fixed at 2.30. If you bet 1 Euro in favor of Arsenal, your profit will be [1 Euro * (2.30-1)] = 1.30 Euros.

– The odd for a draw between the two teams is fixed at 3.40. If you bet 1 Euro for a draw, your profit will be [1 Euro * (3.40-1)] = 2.40 Euros.

– The odd for the victory of AC Milan is set at 3.00. If you bet 1 Euro in favor of AC Milan, your profit will be [1 Euro * (3.00-1)] = 2.00 Euros.

**Odd fractional or English**

The Odd fractional is the most common in the British bookmakers, and has the form of a fraction. The numerator indicates the profit units and the denominator the bet units. To calculate the profit (W), you should use the following formula:* W = amount bet * odd.*

To understand more easily how it works the Odd fractional, let’s examine the same example of a game of the Champions League between Arsenal and AC Milan:

– The odds for Arsenal’s victory is set at 13/10. If you bet 1 Euro in the victory of Arsenal, your profit will be [1 Euro * 13/10 =] 1.30 Euros.

– The odd for a draw between the two teams is set at 12/5. If you bet 1 Euro for a draw, your profit will be [1 Euro * 12/5 =] 2.40 Euros.

– The odd for the victory of AC Milan is set at 2/1. If you bet 1 Euro in the victory of AC Milan, your profit will be [1 Euro * 2/1 =] 2.00 Euros.

**American odd**

The American odd is the most common in the United States bookmakers. The odd normally has a positive or negative value. Are typically odds (probabilities) created for American events such as Baseball, Football, NHL, etc. Negative odds indicate how much you need to invest to get a benefit of 100 units and the positive indicate the corresponding benefit to a bet of 100 units. In decimal, the positive are larger than 2,00 and the negative smaller than said odd. The formulas to be used are as follows:

*For negative odds: W = amount bet * 100 / odd.*

* For positive odds: W = amount bet * odd / 100.*

To understand more easily how it works the Odd American, let’s look at the same example of a game of the Champions League between Arsenal and AC Milan:

– The odds for Arsenal’s victory is fixed at +130. If you bet 1 Euro in the victory of Arsenal, your profit will be [1 Euro * 130/100 =] 1.30 Euros.

– The odd for a draw between the two teams is set at +240. If you bet 1 Euro on a tie, your profit will be [1 Euro * 240/100 =] 2.40 Euros.

– The odd for the victory of AC Milan is set at +200. If you bet 1 Euro in the victory of AC Milan, your profit will be [1 Euro * 200/100 =] 2.00 Euros.

**Odds Classification**

Contrary to what many novice bettors think, not all odds (probabilities) are good to make sports betting. There are Odds calls too low, which must be avoided at all costs, since it does not outweigh the risk potential existing gains. When you find an odd too low, consider not hold your bet, since it will have to bet a lot of money to get a minimally interesting profit. When you bet at very low odds, profit tends to be very low, which means that after losing a bet, losses will be greater than virtually all gains.

1.01 to 1.14. Odds very low

1.15 to 1.49. odds low

1.50 to 1.99. odds medium

+2. odds high

Having this scenario in mind, the ideal is placing bets on medium or high odds, since the risk outweigh the potential gains. One of the betting systems used by most bettors is the** martingale method**, which should be applied for example with medium or high odds, to avoid excessive losses.