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What Is Implied Probability?

Last reviewed 24 August 2026 · Written and checked by the bet.ing editorial team

Implied probability is the chance a price represents: 1 ÷ decimal odds, expressed as a percentage. Odds of 4.00 imply 25%. Because every market includes the bookmaker's margin, implied probabilities always add up to more than 100%, so each one slightly overstates the real chance.

The formula

Implied probability = 1 ÷ decimal odds × 100. Reverse it and you get fair odds: 100 ÷ your percentage. A 40% estimate corresponds to fair decimal odds of 2.50, so anything longer than 2.50 would be value if your 40% is correct.

Why the market totals over 100%

In a fair market the probabilities of all outcomes sum to exactly 100%. Bookmakers price slightly below fair value on every outcome, so the sum comes out higher — commonly 104% to 107% for major sports. The excess is the overround, and it is the source of the house's long-run profit.

To recover the bookmaker's actual view, divide each outcome's implied probability by the market total. In a 2.10 / 3.40 / 3.60 market totalling 104.81%, the 47.62% favourite is really being priced at about 45.4%.

Raw implied probability versus margin-adjusted fair probability in a 104.81% book.
OutcomeOddsImpliedFairFair odds
Home2.1047.62%45.44%2.20
Draw3.4029.41%28.06%3.56
Away3.6027.78%26.50%3.77

Using it to judge a bet

Value exists when your own probability estimate is higher than the price implies. The hard part is not the arithmetic — it is producing an estimate that is genuinely better than a market absorbing money from thousands of participants.

A useful discipline: write down your percentage before you look at the price. If your number only appears after you have seen the odds, it is anchored to them and tells you nothing.

Expected value in one line

EV per unit staked = (your probability × (odds − 1)) − (1 − your probability). At 3.00 with a 40% estimate that is (0.40 × 2) − 0.60 = +0.20, or 20 cents expected profit per euro — if the estimate holds.

Common misreadings

  • Reading implied probability as a forecast. It is a price with margin, not a measurement.
  • Trusting a 1% edge. Your own estimate is rarely accurate to within a percentage point.
  • Ignoring the sum. A price only looks generous until you check what the rest of the market is doing.

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