{"id":7532,"date":"2022-11-10T01:39:29","date_gmt":"2022-11-10T01:39:29","guid":{"rendered":"https:\/\/aceperhead.com\/blog\/?p=7532"},"modified":"2023-06-17T07:13:43","modified_gmt":"2023-06-17T07:13:43","slug":"how-do-bookies-calculate-percentages","status":"publish","type":"post","link":"https:\/\/aceperhead.com\/blog\/pph-guide\/how-do-bookies-calculate-percentages\/","title":{"rendered":"How Do Bookies Calculate Percentages?"},"content":{"rendered":"\n

When bookmakers set their markets for a race or another type of sporting event, their goal is to turn a profit, no matter which team or competitor wins. <\/p>\n\n\n\n

To do so, they have to perfect the art of calculating the book percentage. This can be a tricky step that involves a few different variables and moving parts. In today’s betting guide, we’re sharing how it works and what prospective bookies<\/a> need to know. <\/p>\n\n\n\n

Understanding Book Percentage<\/h2>\n\n\n\n

Any time you discuss the probability that a specific event will happen, you express that likelihood in terms of a percentage. For instance, if you toss a penny into the air, there’s a 50% chance that it will land on heads and a 50% chance that it will land on tails. <\/p>\n\n\n\n

In that case, the book percentage is 100%. In sports betting, we call that a perfect book. However, that’s a simplified example. <\/p>\n\n\n\n

It gets a little trickier when you consider all <\/em>of the possibilities that could occur in a given sporting event. Trying to identify all of those correct odds and adding them up to make 100% can be daunting.<\/p>\n\n\n\n

When a bookie prices up any type of event, they always factor their own profit into the odds. In the betting realm, this is called an overground. <\/p>\n\n\n\n

Naturally, when you add those bookmaker<\/a> percentages into the mix, the cumulative odds will be greater than 100%. In fact, in an average race, the bookmaker’s odds can be upward of 120% or more, depending on the number of participants.<\/p>\n\n\n\n

If there aren’t too many runners, the odds will be lower. This is also the case when there are a few prized horses that are favored to win, and the odds aren’t as evenly spread out.<\/p>\n\n\n\n

Calculating Book Percentage<\/h2>\n\n\n
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\"Book<\/a><\/figure>\n<\/div>\n\n\n

Technically speaking, the book percentage is equal to the reciprocal decimal odds, all added together. Take a horse race, for example. Bookies will take the decimal odds for each horse and divide it into 1. This gives them the reciprocal<\/a> decimal odd for each horse.<\/p>\n\n\n\n

For instance, if the decimal odd is 0.5, they would perform this calculation: 1\/0.5. This gives the reciprocal decimal odd of 2. <\/p>\n\n\n\n

Once they’ve done this for all of the odds, they’ll then add all of the numbers together. Unfortunately, they can’t just add all of the decimal odds up and then<\/em> divide the grand total into 1. They have to calculate each reciprocal decimal odd individually.  <\/p>\n\n\n\n

Racing Example<\/h3>\n\n\n\n

This can be confusing, so let’s work it into a real-life example of a 10-runner race. To find the book percentage of a race, divide 1 by each of these decimal odds. Then, add the sums together. <\/p>\n\n\n\n

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  • Runner 1: 6 (1\/6) = .166<\/li>\n\n\n\n
  • Runner 2: 6 (1\/6) = .166<\/li>\n\n\n\n
  • Runner 3: 6.5 (1\/6.5) = .154<\/li>\n\n\n\n
  • Runner 4: 7 (1\/7) =.143<\/li>\n\n\n\n
  • Runner 5: 7.5 (1\/7.5) = .133<\/li>\n\n\n\n
  • Runner 6: 7.5 (1\/7.5) = .133<\/li>\n\n\n\n
  • Runner 7: 8 (1\/8) = .125<\/li>\n\n\n\n
  • Runner 8: 8 (1\/8) = .125<\/li>\n\n\n\n
  • Runner 9: 8.5 (1\/8.5) = .118<\/li>\n\n\n\n
  • Runner 10: 12 (1\/12) = .083<\/li>\n<\/ul>\n\n\n\n

    Now, add them all up. This gives us a sum of 1.346. To get the book percentage, the last step is to multiply this number by 100, which gives us 134.6%. The bookie’s profit on this race, despite who wins, should be 34.6% if the bets are properly balanced. <\/p>\n\n\n\n

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