Implied Probability: What It Means in Betting
Implied probability is the percentage chance of an outcome as suggested by the betting odds. Every set of odds can be converted into a probability figure, revealing what the bookmaker's price assumes about the likelihood of that result.
Understanding implied probability is one of the most important analytical skills in football betting. It allows you to compare the bookmaker's assessment with your own view and identify situations where the odds may be favourable.
How to Calculate Implied Probability
The formula depends on the odds format you are working with.
From Decimal Odds
Implied Probability = (1 / Decimal Odds) x 100
- Odds of 2.00: (1 / 2.00) x 100 = 50.0%
- Odds of 1.50: (1 / 1.50) x 100 = 66.7%
- Odds of 3.00: (1 / 3.00) x 100 = 33.3%
- Odds of 5.00: (1 / 5.00) x 100 = 20.0%
From Fractional Odds
Implied Probability = Denominator / (Numerator + Denominator) x 100
- Odds of 2/1: 1 / (2 + 1) x 100 = 33.3%
- Odds of 1/2: 2 / (1 + 2) x 100 = 66.7%
- Odds of 5/4: 4 / (5 + 4) x 100 = 44.4%
From American Odds
For minus odds: Odds / (Odds + 100) x 100
- -150: 150 / (150 + 100) x 100 = 60.0%
For plus odds: 100 / (Odds + 100) x 100
- +200: 100 / (200 + 100) x 100 = 33.3%
A Practical Football Example
Consider a Premier League match between Aston Villa and Everton:
| Outcome | Decimal Odds | Implied Probability |
|---|---|---|
| Aston Villa win | 1.75 | 57.1% |
| Draw | 3.60 | 27.8% |
| Everton win | 5.00 | 20.0% |
| Total | 104.9% |
The total exceeds 100%. This is normal, and the extra 4.9% is the bookmaker's overround, which is their built-in margin. The true probabilities of all three outcomes must sum to exactly 100%, so the implied probabilities from the odds slightly overstate the chance of each result.
Why Implied Probability Matters
Implied probability is the bridge between odds and analysis. If you have researched a match and believe Aston Villa have a 65% chance of winning, but the odds imply only 57.1%, there is a gap between your estimate and the bookmaker's price. Bettors who consistently identify these gaps are looking for what is known as "value".
Conversely, if you think Villa's chances are only 50%, the odds imply a higher probability than your estimate, which suggests the price may be too short.
This is an analytical framework, not a guarantee. Past performance does not guarantee future results, and probability estimates are inherently uncertain. However, the discipline of converting odds to probabilities forces you to think in terms of likelihood rather than gut feeling.
The Overround's Impact
Because bookmakers build a margin into their odds, every implied probability is slightly inflated. To estimate the "true" implied probability, you can remove the overround:
True Probability = Implied Probability / Total Implied Probability x 100
Using the Aston Villa example:
- Villa true probability: 57.1 / 104.9 x 100 = 54.4%
- Draw true probability: 27.8 / 104.9 x 100 = 26.5%
- Everton true probability: 20.0 / 104.9 x 100 = 19.1%
These adjusted figures sum to 100% and give a cleaner estimate of the market's view.
Using Implied Probability in Practice
Many football bettors use implied probability to compare bookmaker prices with statistical models. If a Poisson model or expected goals model gives a team a 40% win probability but the bookmaker's odds imply 30%, the discrepancy may be worth investigating further.
It is also useful for comparing odds across bookmakers. Two bookmakers might offer different odds on the same match, and converting both to implied probability makes the difference immediately visible.
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