Football betting odds convert to implied probability, worked through one Premier League match

Most football bettors know how to read odds as returns. If an EPL team has 1.50 odds of winning, a £100 bet would return £150 in total if successful, including £50 profit. In short, betting odds determine the exact returns if the bet is successful.

However, most punters don’t know how to translate odds into probabilities. Understanding how implied probability works can bridge the gap between the betting odds and the likelihood of an event happening. The concept also shows how the bookmaker’s margin is built into every price.

Meaning of Implied Probability in Football Betting

Prediction sites sometimes show win probabilities. For example, Team A might be given a 70 percent chance of winning, Team B 12 percent and the draw 18 percent — the three outcomes available in football betting on a match like this.

Implied probability works in the opposite direction. Bettors can convert market odds back into percentages, while bookmakers generally start from probability estimates and incorporate a margin when setting their prices. Implied probability depicts the likelihood that an event will occur based on the betting odds. Remember, that’s not a promise but a probability.

The Maths Behind Implied Probability with Arsenal vs Leeds as an Example

UK bookmakers mostly list their odds in Fractional, Decimal, and American formats. The first two are the most popular among UK bettors. In Fractional odds, the left number (numerator) is the profit, whereas the right number (denominator) is the stake amount. So, 4/1 odds mean each £1 staked wins £4 profit, returning £5 in total including the original stake.

Decimal Odds:

In Decimal odds, the implied probability as a percentage is (1/odds) × 100. Using illustrative odds for Arsenal vs Leeds, Arsenal are the favourites at 1.35. The implied chance is therefore 1/1.35 × 100 = 74.07 percent. Decimal odds are the most direct way to calculate implied percentages because the price already reflects the total return multiplier.

Fractional Odds:

In the Fractional format, the implied chance equals the denominator/(denominator + numerator). Sticking with our EPL example, Arsenal are the favourites at 7/20 odds. Therefore, the implied probability of Arsenal winning is 20/(7+20) = 74.07 percent.

These examples show that the implied chance is consistent in Decimal and Fractional odds. That’s because odds formats are just different ways of expressing the same probability of an event occurring.

Why Implied Probabilities Exceed 100%

The true probabilities of the three possible outcomes must add up to 100 percent. In our example, the implied chance of Leeds winning is 13.33 percent (1/7.50 × 100), whereas the chance of a draw is 20 percent (1/5.00 × 100). The total implied chance is 107.4 percent.

In betting, the extra 7.4 percent is the market overround, or vigorish. Oddsmakers build this margin into their prices so that, across all outcomes, the odds favour the bookmaker. It’s why bookmaker-implied probabilities are not a set of probability estimates that should add up to 100 percent. Instead, these values represent the prices for each market, with each price containing the bookmaker’s margin.

The overround can also be removed proportionally. Arsenal’s 74.07 percent implied probability divided by 107.4 percent gives a margin-free market estimate of about 69.0 percent, equivalent to fair odds of roughly 1.45.

Market-Implied Probability is Not Your Estimate

Implied probability is only one part of the picture. Knowing what the bookmakers think isn’t the same as predicting what could actually happen. That’s where your estimated probability comes in. This rate represents your independent assessment of what could happen in the game.

Let’s go back to Arsenal’s 74.07 percent implied chance. A few hours before the game, the manager announces that their two starting centre-backs are out with injuries. Leeds’ centre-forward, meanwhile, is on a scoring streak. Suppose those developments lower your own estimate of Arsenal’s winning chance to 65 percent.

That is below both the raw 74.07 percent implied by the 1.35 price and the margin-free market estimate of about 69 percent.

The comparison shows how different assumptions can produce different views of the same price, not whether a particular bet will be profitable. The gap between 65 percent and the raw implied probability is 9.07 percentage points, but any personal estimate remains uncertain.

The bookmaker margin also means bettors as a group lose money over time.
 

In Closing

Overall, implied probability expresses the probability embedded in a market price. It is not the same as an independent estimate of what may happen. The implied probability comes from the odds, while a personal estimate comes from separate analysis and remains uncertain. Published prices also contain the bookmaker’s overround.

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