Understanding odds
Every posted odd contains an invisible commission. It appears nowhere, no bookmaker publishes it, and yet it decides whether you can win over time. The calculation fits on one line.
In short: a bookmaker's margin is the commission built into its odds. You calculate it by adding up the inverse of each price, then subtracting 1. On a 1X2 market it runs 2 to 4% at competitive operators, 5 to 7% at the market average, and turns clearly unfavourable above 8%. It is taken on every bet, winning or losing.
An odd expresses a probability. An odd of 2.00 means one chance in two, an odd of 4.00 one chance in four. Simply divide 1 by the odd to obtain this implied probability.
Now add the probabilities of a match's three outcomes — win, draw, loss. Logically the total should come to exactly 100%: one of the three is bound to happen. Yet it always exceeds 100%.
That excess is the margin. It is the share the bookmaker takes for itself in advance, whatever the result of the match.
Take a real match, with ordinary odds:
Three steps, valid on any match:
Change the odds above. Leave “N” empty for a match without a draw (tennis, basketball).
The full formula: add the inverse of each odd, then subtract 1. Here, 1.05 − 1 = 0.05, or 5%.
The bookmaker shows the favourite at 52.6%. But remove the margin to bring the total back to 100%, and its true estimate drops to 50,1 %. The 2.5-point gap is not an error: it is its fee, taken out of your stake.
It varies widely by operator, league and bet type. Benchmarks for 1X2 in the major leagues:
| Margin | Reading |
|---|---|
| 2 – 4 % | Very competitive: the price is close to fair |
| 5 – 7 % | Market average |
| 8% and above | Clearly unfavourable to the bettor |
Two rules hold almost always: the margin rises on secondary competitions, where operators are less sure of their prices; and it explodes on side markets — goalscorers, corners, cards — where it frequently exceeds 15%.
The formula does not change when the market has only two outcomes: over or under 2.5 goals, both teams to score, a tennis or basketball match. You simply add two probabilities instead of three.
Take two odds of 1.90 on “over 2.5 goals” and “under 2.5 goals”. Each is worth 52.6%, the total is 105.3%, so a 5.3% margin. With no commission, both odds would be 2.00. Keep this benchmark in mind: on a balanced two-way market, two odds below 2.00 are enough to give the margin away.
In short: the winning margin is a type of bet, not a commission. You predict the winner and the number of goals it wins by: “team 1 by 1 goal”, “team 1 by 2 goals”, “team 1 by 3 goals or more”, “draw”, then the same choices for team 2.
Despite the name, it has nothing to do with the bookmaker margin described above. Here the word refers to the gap in the final score. Depending on the operator, the options are shortened to codes of letters and numbers; the number 1 almost always refers to the home team, 2 to the away team, and the number after it to the goal difference.
It is also one of the bets where the bookmaker takes the most. The market has seven outcomes instead of three, and the margin hides in every one of them. With typical example odds:
| Outcome | Odds | Implied probability |
|---|---|---|
| Team 1 by 1 goal | 4.00 | 25.0% |
| Team 1 by 2 goals | 6.00 | 16.7% |
| Team 1 by 3 goals or more | 8.00 | 12.5% |
| Draw | 3.40 | 29.4% |
| Team 2 by 1 goal | 5.00 | 20.0% |
| Team 2 by 2 goals | 10.00 | 10.0% |
| Team 2 by 3 goals or more | 15.00 | 6.7% |
The total reaches 120.2%: the margin exceeds 20%, four times that of an ordinary 1X2. The calculation is the same as above, applied to every outcome in the market. It is the side-market rule taken to the extreme: the more finely a market is sliced, the more each slice costs.
This is what most bettors find out too late: the margin is taken on every bet, winning or losing. It does not wait for you to be wrong.
A telling example: across nearly 9,000 bets simulated from real closing odds, a method that simply follows the market favourite wins about six times out of ten — and still loses money. The hit rate is good; the margin eats it.
Our league pages give each licensed operator's average margin on upcoming matches, so you can compare a major league with a smaller one (in French): Serie A, Bundesliga, Eredivisie, Championship, Liga Portugal, Ligue des Champions.
Being right often is therefore not enough. That is why a hit rate shown on its own, without the return that goes with it, means nothing.
On every match analysed, we compare the odds of several bookmakers, isolate the margin built into the price and recompute the real probability of each outcome. No bet is taken on the site, and no payment comes from bookmakers.
See today's analysesNo, and the gaps are substantial. On the same match it commonly varies twofold from one operator to another. It is the simplest lever available to a bettor, and the one most often ignored.
Not at a traditional bookmaker: it is built into the posted price and there is no way around it. Betting exchanges work on a commission rather than a margin, but a cost remains either way.
No. A low margin only means you start with a smaller handicap. It improves your chances over time; it does not create them.
The calculation above applied live to every operator, on upcoming matches: a ranking by margin actually observed.
See the margin comparisonEvery Friday morning, before the weekend's football: an honest record of the week, misses included, and the French-licensed operator taking the least on the upcoming matches. Free, one email a week (in French), one-click unsubscribe.
MARGE publishes statistical analysis for information only. We are not a betting operator, we accept no bets and we receive no payment from bookmakers. No analysis constitutes advice or a guarantee of any result. Sports betting carries a risk of real financial loss and is forbidden to minors. If gambling is causing you difficulty, free and confidential help is available in France on 09 74 75 13 13 (Joueurs Info Service), and in the United Kingdom from GamCare on 0808 8020 133.
Home · Margin comparison · Are tipsters profitable? · Value bet: definition and calculation · Margin calculator · Convert odds · Today's predictions · Our method and results