The following are the results of a 2023 bookmaker margins and markets survey. The survey is split into racing and sports surveys.
Table of Contents
This article is lengthy, so shortcuts are provided below for those who are only interested in certain sections.
- What are bookmaker margins?
- How to calculate bookmaker margins
- How to interpret bookmaker margins
- Bookmaker margin vs. vigorish (vig)
- The value of combined margins
- Racing margins survey results
- Sports margins survey results
- Sports markets survey results
- Odds comparison tool
- Survey caveats
What are Bookmaker Margins?
The bookmaker margin, also known as the overround, the cut or the take, is the hidden amount charged by a bookmaker for accepting a wager.
When a bookmaker sets the odds they first estimate the probability of each possible outcome. In a fair coin toss, for example, the probability of heads is 50%. When using the decimal/European odds system the fair odds, also known as the true odds, equal the reciprocal of the bookmaker’s estimated probability, in this case 1 / 50% = 2.00. To fund their services, the bookmaker adjusts these odds downward to create a profit margin. Typical odds on a selection with a 50% chance of winning are 1.91. The gap between the bookmaker’s odds (1.91) and the fair odds (2.00) is due to the bookmaker margin.
The bookmaker margin is a measure of the bookmaker’s profit margin for an event and is a hidden transaction cost for punters. This profit is how bookmakers finance their services but bookmakers vary in the margins they apply. From a punter’s perspective, the lower the margin, the better. The difference between 1.90 and 1.92 line odds may not seem significant for a single wager, but when betting repeatedly this difference has a compounding effect. This can make the difference between winning and losing money in the long-term.
How to Calculate Bookmaker Margins
When using decimal odds the bookmaker margin equals the sum of the reciprocals of the odds, minus 1. Below are calculation examples using two-outcome and three-outcome events.
The margin is amount by which the market exceeds 100%.
For a 100.0% market the margin is zero. If you compile the best available odds across a number of bookmakers and the combined market is below 100.0%, then the margin is negative, which means an arbitrage opportunity may exist.
How To Interpret Bookmaker Margins
The margin measures the bookmaker’s profit if they were to receive wagers on each outcome in proportion to the odds. Suppose a bookmaker offers decimal odds a on outcome A and odds b on outcome B. If proportion b/(a+b) is wagered on outcome A and a/(a+b) is wagered on outcome B, then the bookmaker will receive the same profit regardless of the result.
For example, recall that the bookmaker margin for the two-outcome event above was 3.5%. Suppose $100,000 in total is wagered on the market, with:
(1.64/(1.64 + 2.35)) x $100,000 = $41,102.76 wagered on Oklahoma City and
(2.35/(1.64 + 2.35)) x $100,000 = $58,897.24 wagered on Denver.
Depending on the outcome, the bookmaker will pay out one of the following two amounts:
If Oklahoma City wins: $41,102.75 x 2.35 = $96,591.48
If Denver wins: $58,897.24 x 1.64 = $96,591.48
The bookmaker accepts $100,000 in wagers but only pays out $96,591.48 to the winners. The profit margin is ($100,000 – $96,591.48)/$96,591.48 = 3.5%, as calculated by the margin earlier.
To provide perspective on how odds relate to margins, the table on the right compares equal line odds (bets with a 50% chance of winning) to their respective margins. Note that 2.00 line odds equate to a margin of 0%, where the bookmaker makes no profit on the market.
Bookmaker Margin vs. Vigorish (Vig)
Another popular term, particularly in the United States, for measuring the bookmaker profit margin is vigorish. It is often referred to as vig, for short, or juice. In the context of this article the term vigorish refers to a different calculation to bookmaker margin. In short, the bookmaker margin is the bookmaker’s profit margin relative to the payouts to the winners, while vigorish refers to the profit margin relative to turnover, i.e. the initial wagers. Because the total payout is always less than the total turnover, the bookmaker margin is greater than vigorish for positive margins.
Unfortunately there are conflicting definitions of bookmaker margin and vigorish. Even on Wikipedia the explanation of how to calculate vigorish depends on which article you visit. This survey uses the definition of bookmaker margin (overround) as used in the Mathematics of bookmaking Wikipedia article and the definition of vigorish as used in the Vigorish Wikipedia article.
Referring to the previous NBA example:
The bookmaker margin is 1/1.64 + 1/2.35 – 1 = 3.53%
while vigorish is (1 – 1.64*2.35/(1.64 + 2.35)) = 3.41%
Recall that with this example, if $41,102.76 is wagered on Oklahoma City and $58,897.24 is wagered on Denver, the bookmaker accepts $100,000 in wagers and pays out $96,591.48 to the winners, regardless of the result. The bookmaker margin is ($100,000 – $96,591.48)/$96,591.48 = 3.53%, while vigorish is ($100,000 – $96,591.48)/$100,000 = 3.41%.
Both of these measures of bookmaker profit margin are valid, providing you understand what each represents. You can think of bookmaker margin as metres and vigorish as yards.
Note that if the bookmaker margin is 0% then vigorish is also 0%. If one is negative then so is the other.
The choice of bookmaker margin over vigorish has no impact on this survey. If the bookmaker margin of one bookmaker is higher than another’s, then the same can be said for that bookmaker’s vigorish. The relative value between bookmakers is the focus of this survey, not the actual values.
To understand more about bookmaker margins and vigorish, check out our bookmaker margin / vigorish calculator.
The Value of Combined Margins
For each market a “combined” margin is calculated by sourcing the best available odds across the surveyed bookmakers. This combined margin represents the attainable margin that can be achieved through holding a portfolio of bookmaker memberships and shopping around for the highest odds.
The combined margin is always equal to or lower than the lowest bookmaker’s margin. The greater the disparity between the odds of two or more bookmakers, the lower the combined margin will be.
For example, for Game 3 of the 2023 State of Origin we observed the following head-to-head markets:
The bookmaker margin for BoomBet is 4.3% while the margin for Bet Right is 5.3%.
If we combine the two markets by sourcing the best available odds we get:
The combined margin for this market is 1/2.44 + 1/1.67 – 1 = 0.9%.
Combined margins are a crucial for beating bookmakers because they lower the hurdle rate that is required to achieve a profit. The equivalent line odds for the 4.3% margin at BoomBet is 1.92. To make a profit on 1.92 odds you would have to win more than 52.1% of the time. In contrast, the equivalent line odds for the 0.9% combined margin is 1.98. To make a profit on 1.98 odds you would only need to win more than 50.4% of the time.
Note that if the combined margin is a negative number then an arbitrage opportunity exists.
Racing Margins Survey Results
Fixed win odds were recorded for a random selection of thoroughbred, harness and greyhound races. For thoroughbreds, this included everything from races in the middle of the racecard on weekdays through to Group 1 races on Saturday. The odds were recorded on the day of each race. Some were recorded before the first race of the racecard, while others were recorded with just one race left to run at that racecourse prior to the race jump.
The average of the win margins are shown in the tables below, along with the frequency with with each bookmaker offered the (equal) best available odds for each runner.
The Overall Racing Margins table combines the averaged data across the three racing types.
Note that the actual margins are of less interest than the relative margins between the bookmakers. This is because the margins will vary depending on the number of runners and the race prestige.
The nature of the race played a large roll in the odds competitiveness. bet365 offered the best odds on 79% of the runners on the surveyed Group 1 races, compared to 24% for all other races.
One standout is BoomBet. They didn’t offer the best margins but they did offer the best odds on 36% of the runners. For the non-Group 1 races in the survey, BoomBet offered the best odds on a whopping 51% of the runners.
The results highlight the benefit of having multiple bookmaker memberships. By selecting the best available odds the margin dropped to 19.0%, compared to 26.6% for Colossalbet.
Colossalbet and Picklebet again came out on top, but this time by a larger degree. They also dominated for the frequency of offering the best available odds on each runner. Their margin of 27.7% was closer to the combined margin of 24.9%, compared to the results for thoroughbreds. This suggests there is less value in holding multiple bookmaker memberships for fixed greyhounds racing than there is for fixed thoroughbreds racing.
Across the board, bookmakers had higher greyhounds margins than they did for thoroughbreds. SportChamps in particular were notably less competitive for greyhounds odds than they were for thoroughbred racing.
BoomBet was again a standout. While they didn’t offer the best margins, they did offer the best odds on 38% of the runners.
Picklebet didn’t score the same as Colossalbet because, while they did offer the same odds, we encountered races where Colossalbet offered fixed odds while Picklebet had yet to list them. Colossalbet again came out on top, both for the margin and for the frequency of offering the best odds. Picklebet had a lower best odds frequency due to not having fixed odds yet available for certain races during the survey.
The Colossalbet margin of 26.3% was closer to the combined margin of 23.5%, compared to the results for thoroughbreds. This suggests there is less value in holding multiple bookmaker memberships for fixed harness racing than there is for fixed thoroughbred racing.
SportChamps stood out for being much less competitive for harness odds than they were for thoroughbred racing.
Once again, BoomBet was a standout. While they didn’t offer the best margins, they did offer the best odds on 44% of the runners.
Overall Racing Margins
Colossalbet came out on top, both in terms of margins and the frequency with which they offered the best available odds on runners.
Despite employing higher margins, BoomBet performed incredibly well when it came to offering the best odds on particular runners. This highlights the fact that bookmaker margins tell only half the story. Margins can be heavily inflated if a bookmaker offers notably lower odds for a few selections, even if that bookmaker offers good value on the remaining runners. A bookmaker can employ higher margins but still be worth including in a portfolio of memberships if they frequently offer the best odds on certain selections. BoomBet is a classic example of this.
Sports Margins Survey Results
The following leagues and markets were included in the survey:
AFL: head-to-head, line, total score
A-League: head-to-head, over/under 2.5 goals
ATP tennis: head-to-head
EPL: head-to-head, over/under 2.5 goals
MLB: head-to-head, line, total score
NHL: head-to-head, line, total score
NBA: head-to-head, line, total score
NRL: head-to-head, line, total score
State of Origin: head-to-head, line, total score
Super Rugby: head-to-head, line, total score
The odds were typically recorded within 24 hours of the events commencing.
The table below provides the average margins for the surveyed leagues. The “Equiv. Line” column shows the equivalent line odds for the respective margins.
Note that the actual margins are of less interest than the relative margins between the bookmakers. This is because margins will vary depending on the leagues and markets chosen.
bet365 came out well on top with a 4.9% average margin. They were particularly strong for the MLB and NHL, with average margins of 4.2% and 3.6%, respectively. bet365 also dominated for the frequency with which they offered the best odds for a particular selection.
The combined margin of 3.1% highlights the benefit of holding multiple bookmaker memberships. This margin is considerably lower than 4.9% for bet365 and 5.8% for the survey average.
The bookmakers had different strengths, depending on the market. PlayUp finished 4th overall, but they recorded the second best margins for line markets. Colossalbet finished 6th overall, but they recorded the third best margins for totals markets.
Sports Markets Survey Results
Whilst surveying the odds, we also tallied the number of markets per fixture. For example, if a bookmaker offered head-to-head, line and total score markets for a game, then the number of markets for that fixture is three.
For this survey we only counted up to 50 because beyond that number you tend to just get obscure markets. Also, bookmakers can vary in the way they count markets so there may not be a substantial difference between, say 80 markets and 120 if the first bookmaker counts a “Pick Your Own Line” section as one market, while the second bookmaker counts each line (-7.5, -6.5, -5.5, etc.) as a separate market.
Much like in the odds survey, the actual market numbers are less relevant due to the arbitrary nature of the sports and leagues chosen. The focus here is on the relative averages between the surveyed bookmakers.
The table below provides the average number of markets per fixture that we observed during the survey. An equal weighting was given to each league surveyed.
Sports Markets Survey
The broad range of markets provided by these three bookmakers makes them suitable for anyone looking for a solitary bookmaker membership. A casual sports punter will likely find that most, if not all, of the bookmakers would suit their needs.
Colossalbet dominated the fixed odds racing survey. They came out on top for both the margin and the frequency for which they offered the best odds on specific runners. Picklebet also performed well due to having the same odds as Colossalbet, however we did observe instances where Picklebet had yet to post a fixed odds market, while Colossalbet already had.
bet365 was the clear next best for racing.
The most interesting result was BoomBet, who featured strongly for the frequency of offering the best odds for particular runners, despite having higher margins. This highlights the fact that odds only show part of the story. A bookmaker can offer great value odds on particular runners, but still have higher margins if they offer less value on a few other runners. Due to their higher margins, BoomBet is not ideal for a standalone membership for fixed odds betting, but they are definitely worth including in a portfolio of memberships for the purpose of odds shopping.
bet365 was the clear winner in the sports odds survey, with Unibet the clear runner up. bet365 dominated not only for having the best margins, but for also offering the greatest selection of markets per fixture.
The survey results highlight the benefit of having multiple memberships, which enables you to shop around for the best odds.
For sports we achieved an average margin of 3.1% by shopping around for odds. This is substantially lower than the best performing bookmaker at 4.9%, and the survey average of 5.8%.
For racing the benefits were greater for thoroughbreds than for greyhounds and harness. For thoroughbred racing the combined margin was 19.0%, compared to 26.6% for Colossalbet. For greyhounds the combined margin was 24.9%, compared to 27.7% for Colossalbet, and for harness racing the combined margin was 23.5%, compared to 26.3% for Colossalbet.
Odds Comparison Tool
You can compare bookmaker odds for upcoming fixtures in the Bookmaker Odds Comparison section.
The surveyed margins were heavily dependent on the sample of sporting events chosen. Comparative margin levels may change over time and they will differ for sports and leagues not covered in the survey.
This survey focused on the margins and markets shortly before the event start. Bookmakers vary in their approach to margins and markets in the week leading up to a fixture. It’s not unusual for the margins to be higher on Monday for a Saturday fixture than on Friday. Some bookmakers offer a strong selection of markets soon before the event, but are slow to provide those markets. bet365 is an example of a bookmaker that makes markets available earlier than the competition.
This survey focused on margins and the number of markets per fixture, but a key caveat is that betting limits are ignored. Furthermore, some bookmakers offer higher limits but may limit or close your account if you regularly win with high-stakes wagers. In addition, some bookmakers offer frequent promotions in lieu of lower odds, which is not factored into these results.