Sportsbook

Implied probability: the chance built into the price

Implied probability (implied chance) is the chance of an outcome built into the price: 1 / decimal odds. Odds of 1.90 mean 52.6%. Across a market these probabilities add up to more than 100%, and the difference is the bookmaker margin.

Yevhen SychovOctober 2026

Formula and example

Implied probability = 1 / decimal oddsTwo outcomes at 1.90: 1 / 1.90 = 52.6% each, 105.3% in total. The extra 5.3% is the margin.

At a single bookmaker the market total is above 100%, because a margin is built into the price of every outcome. The fair probability is found by dividing by the total: 52.6% / 105.3% = 50%.

Fractional and American odds are first converted to decimal: 3/2 and +150 are 2.50, which is 40%.

How to use it

  • Bet value. If the real chance is higher than the one in the price, the bet has positive value. Odds of 2.50 mean 40%, while the real chance is, say, 45%: a €100 bet earns the player €12.50 on average, that is 45% of €250 minus €100.
  • Profiling strong players. A sharp consistently buys probability cheaper than the market. They took 2.10, which is 47.6%, and by the start the price had dropped to 1.95, which is 51.3%: they bought the chance cheaper than the market valued it.
  • Arbs. If the probabilities at the best prices across different bookmakers add up to less than 100%, that is an arb, and your price in it has usually lagged behind the market.
  • Promo cost. The cost of a boost or a free bet is calculated through the probability of the outcome, not at face value.

Common mistakes

  • Treating 1 / odds as the fair probability. It contains the margin, which is why the market total is above 100%.
  • Splitting the margin equally. There is often more of it in the outsider's price than in the favourite's, so dividing by the total gives only an approximate fair probability.
  • Judging a player by their winnings. What matters is the probability they bet at compared with the closing line, not how much they won in a month.
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