All about bookmakers’ odds

Bettors are often interested in how bookmakers determine odds for specific markets. Each betting organizer wants to earn their own percentage (margin) on betting options.

Quotes are also affected by the amounts of players that they allocate to a particular position. Is there a human factor when setting coefficients? Quotes are set by a person or a program? We will answer these questions in our review.

What do the odds in bookmakers mean?

Even inexperienced players know that the coefficient determines the win. This is a multiplier for the bet size. The product of these numbers is the bettor’s win. Bookmakers put a margin or commission into all quotes. Within one painting, the bookmaker’s earnings may differ by several percent.

There is a formula by which the bookmaker’s margin is determined for two and three outcomes. If the event has two possible outcomes, for example, the victory of tennis players, then the formula for calculating the margin is as follows:

M= (100/K1+100/K2) — 100

Here, K1 and K2 are the bookmaker’s odds for each option. What are these events? These are fractional totals, P1 and P2 without taking into account draws in different sports, even and odd totals in basketball, football, tennis, hockey and other disciplines. There are a lot of two-variant bets on whether the event will take place or not: penalty shootout, elimination in football – yes/no, tie-break in tennis – yes/no, overtime in hockey, basketball – yes/no. For each such market, a margin calculation formula with two coefficients is applicable.

A similar formula is used to determine the margin for three outcomes. Another term is added:

M= (100/K1+100/K2 + 100/K3) — 100

What are the coefficients

  • Decimals. The most common type. To calculate the winnings, you need to multiply the bet amount by the coefficient. For example, if you put 100 rubles on 1.8, then the net profit will be 80 rubles.
  • British (fractional) coefficients. They are quite rare in the modern line. Determine the profit that the player will receive for each ruble. For example, if you bet 50 rubles on the 3/5 coefficient, then the potential gain will be 30 rubles.
  • American coefficients. They represent positive or negative numbers that are placed near the opponents. It seems that it is quite difficult to understand them, but this is an erroneous opinion. A negative number is placed opposite the favorite, and a positive number is placed near the outsider. The profit is calculated quite simply. For example, the bookmaker accepts bets on the victory of team «A» with a coefficient of -135, and on the victory of team «B» – 135. If you bet 100 rubles on the first opponent, you will win 35 rubles of net profit. A bet of a similar amount on an outsider will bring a win of 135 rubles.

Why are the coefficients constantly changing?

After calculating the coefficients and laying the margin, the office does not stop influencing the values. First of all, the change in quotes is affected by the players’ bets. If a large flow of funds is concentrated on one outcome, the coefficient for this market is significantly reduced, and for the opposite – increases.

There may be other reasons for the movement of the line, which are associated with the appearance of new information. For example, a key performer has been injured in the team, a coach has changed, or rainy weather is expected. These factors affect both the outcome and the number of goals and other indicators of the game.


Odds are the most important value in all bookmakers. You can use the decimal (European) coefficient model, American or fractional (British), depending on how you are more comfortable.

With the help of coefficients, you can calculate the potential profit from each bet. The coefficients may vary, pay attention to this. The higher this indicator, the less likely (according to the bookmaker) the bet will pass.