Football's three-way market: finding the margin and the fair odds
Odds and margins
Home 2.50, draw 3.30 and away 2.90 imply 4.79% more than 100% in total: a margin of 4.57%. Without it the fair odds are 2.62, 3.46 and 3.04.
- 4.57%margin
- 2.62fair home odds
- 3.46fair draw odds
Understanding the Overround
The sum of implied probabilities from the offered prices exceeds the total probability space. This excess is the bookmaker's margin. The table below shows how the offered odds for home, draw, and away compare to their fair counterparts. The overround is larger than the margin itself because the calculation involves reciprocal sums. The margin represents the cost of placing a bet, while the fair odds represent the true probability adjusted for that cost. You can verify these calculations using the margin calculator.
| Outcome | Offered | Fair |
|---|---|---|
| Home | 2.50 | 2.62 |
| Draw | 3.30 | 3.46 |
| Away | 2.90 | 3.04 |
Calculating Fair Odds
To find fair odds, divide each offered price by the total implied probability. This normalizes the values so they sum to the full probability space. For example, the fair odds for a home win are higher than the offered price because the margin is removed. The fair odds for a draw are larger than those for a home win, reflecting its lower probability. Similarly, the fair odds for an away win are larger than those for a home win. These adjustments ensure that the probabilities add up correctly without the extra cost. The process is straightforward and relies on basic arithmetic rather than complex models.
Comparing Outcome Probabilities
The fair odds reveal the relative likelihood of each outcome. A draw has higher fair odds than both home and away wins, indicating it is less likely to occur. The away win has higher fair odds than the home win, suggesting the home team is favored. These relationships remain consistent whether you look at offered or fair odds. The margin affects the absolute values but not the relative order of probabilities. Recognizing these patterns helps you assess value without relying on external tips. The table above summarizes these differences clearly. For further assistance with calculations, consult the help section.
Questions
Why are fair odds higher than offered odds?
Fair odds remove the bookmaker's margin. Since the margin reduces the payout, removing it increases the odds to reflect the true probability of each outcome.
Does a lower margin mean better value?
Yes. A lower margin means less cost per bet. The player retains a larger portion of their stake over time compared to markets with higher margins.
How do I calculate fair odds myself?
Sum the reciprocals of the offered odds. Divide each individual offered odd by this total sum. The result is the fair odd for that outcome.
Every figure on this page is computed by code from exact fractions for odds, margins and parlays, and closed-form Kelly growth, each checked by a seeded simulation. See the methodology.