Маржа букмекера
Bookmaker Margin
Bookmaker margin is the built-in edge a bookmaker builds into its odds, allowing it to earn from the betting book regardless of how events turn out.
What is Маржа букмекера (Bookmaker Margin)?
Bookmaker margin (overround, bookmaker commission) is the amount by which the sum of implied probabilities of all outcomes exceeds 100%. If the bookmaker spreads a 100% probability across outcomes with an upward markup, the difference is its margin. It is built into every odds value and is the main source of bookmaker income in sports betting.
## How it works
Odds are converted to probability using the formula 1 / odds. For a fair book, the sum of these probabilities across all outcomes of an event equals 100%. A bookmaker's sum comes out above 100%, and the excess is the margin. For example, with two outcomes priced at 1.95 and 1.95, the probabilities add up to about 102.6%, meaning a margin of about 2.6%.
## Where it appears and what it affects
Margin varies by sport, market and league: it is usually lower on mass-market events and often higher on niche events and live betting. The higher the margin, the harder it is for a bettor or tipster to make a profit over the long run. For arbitrageurs, the margin determines how profitable an arbitrage deal is and how much remains after commissions.
## Common mistakes
A typical mistake among practitioners is comparing odds without recalculating the margin. Two bookmakers may offer identical odds on a win but differ in margin on other outcomes. Another mistake is confusing margin with hold or GGR: margin applies to a specific market, while GGR reflects actual turnover and payouts.
FAQ
Are bookmaker margin and commission the same thing?
In essence, yes: both refer to the gap between the real probability of an outcome and what the bookmaker builds into the odds. 'Commission' is used in everyday speech, while 'margin' and overround are used in analytics.
How can I quickly calculate the margin from odds?
Convert each odds value to probability as 1 / odds, add the results across all outcomes of the market, and subtract 1 (or 100%). The resulting difference is the margin.
Can the margin be eliminated completely?
In a regular betting book, margin is always present, otherwise the bookmaker would have no economic model. It can only be avoided by choosing markets and bookmakers with a lower margin, or by using arbitrage when the combined margin falls below 100%.