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Margin calculator: bookmaker margin & fair odds
Enter the odds of every outcome in one market. The calculator shows how much the bookmaker builds into the prices, what share of stakes the market pays back, and what the odds would be without the margin.
This market
- Implied probabilities in total
- 105.60%
- Payout
- 94.69%
Fair odds
| # | Odds | Implied | Fair probability | Fair odds |
|---|---|---|---|---|
| Outcome 1 | 2.10 | 47.6% | 45.1% | 2.22 |
| Outcome 2 | 3.40 | 29.4% | 27.9% | 3.59 |
| Outcome 3 | 3.50 | 28.6% | 27.1% | 3.70 |
How to read your result
Bookmaker margin is how far the implied probabilities of all outcomes add up above 100%. A fair coin toss priced 2.00 and 2.00 adds up to exactly 100%; the same toss priced 1.90 and 1.90 adds up to 105.3%, and the extra 5.3 points are the margin.
Payout is the same prices seen from your side: 100% divided by that total. It is the share of stakes the market returns to bettors on average, if the fair odds are right. Fair odds are the prices with the margin taken out, one per outcome, and the fair probability next to them is what those odds stand for.
Compare a market with the same market at other bookmakers rather than with a different market: a three-way match result or a long outright list has more outcomes to spread the margin over than a two-way total. A total below 100% never comes from one bookmaker's market; it means the prices were taken from different bookmakers, or one was typed wrong.
How the calculator works
margin = 1/odds₁ + 1/odds₂ + … + 1/oddsₙ − 1
payout = 100% ÷ (1/odds₁ + 1/odds₂ + … + 1/oddsₙ)
fair odds = 1 ÷ fair probability
The margin and the payout follow from the odds alone. Fair odds need one more decision: how the bookmaker spread the margin across the outcomes. The calculator offers three methods, chosen with the switch under the odds:
- Multiplicative
- Each implied probability is divided by their total, so every outcome gives up the same share. It is the standard method and the one behind our value bets and the odds methodology.
- Power
- Each implied probability is raised to the same power, chosen so that the results add up to 100%. Long shots give up more than favourites, in line with the favourite–long-shot bias that betting research has found in many markets.
- Shin
- Hyun Song Shin's model (1993) assumes that part of the money comes from bettors with inside information and solves for that share. Like the power method it takes more from long shots. When the prices carry no margin it gives the multiplicative answer.
The calculation runs in your browser and the odds you type are not sent anywhere. Odds are read to three decimal places, and a market can have from 2 to 20 outcomes: enough for a match result, a total, a handicap or a short outright list.
Worked example
Take a match result priced 2.10 for the home win, 3.40 for the draw and 3.50 for the away win, the market from our odds methodology. The home price implies 47.6%. The three implied probabilities add up to 105.6%, so the margin is 5.6% and the payout 94.7%.
With the multiplicative method the home win's fair probability is 45.1%, and the fair odds are 2.22 for the home win, 3.59 for the draw and 3.70 for the away win. A price above the fair odds at another bookmaker beats the market's own estimate; a price below it is the margin at work.
Where the three methods disagree
On a balanced market the three methods give nearly the same answer. They part company when a strong favourite meets long shots. In a market priced 1.25, 5.50 and 13.00 (margin 5.9%), the long shot's fair odds are 13.76 with the multiplicative method, 16.45 with the power method and 16.21 with Shin's.
That gap matters when you judge long-shot prices: the multiplicative method assumes the long shot carries only its proportional share of the margin, so a price that looks close to fair may not be. If the market has a clear favourite, check the other two methods before you read anything into a long-shot price.
Stake tax and fees
In Poland 12% of every stake is tax, so only the rest is in play; in Croatia operators deduct a 5% fee from every stake. Choose the country to see the payout after that deduction: the example market's 94.7% becomes 83.3% in Poland and 90.0% in Croatia. The margin and the fair odds stay the same, because the deduction changes what you get back, not the probabilities.
Winnings tax depends on how much you win, so it is not part of the payout here; the bet calculator works it out for a given stake. Czechia and Slovakia deduct nothing from stakes or winnings.
Questions
- What is a bookmaker's margin?
- The amount by which the implied probabilities of a market's outcomes add up above 100%. It is built into the odds, and it is how a bookmaker earns whatever the result.
- How do I calculate the margin from odds?
- Add up 1 ÷ odds for every outcome and subtract 1. For odds of 2.10, 3.40 and 3.50 the total is 105.6%, so the margin is 5.6%.
- What is the difference between margin and payout?
- They describe the same prices from two sides. Payout is 100% divided by the sum of implied probabilities, so a margin of 5.6% is a payout of 94.7%.
- Which method should I use?
- The multiplicative method for a quick, standard answer and for evenly matched outcomes; the power or Shin method when one outcome is a strong favourite and the long shots are what you are pricing.