Implied probability: convert decimal odds to percentages
Convert decimal odds with 1 / odds, calculate payouts and distinguish bookmaker prices from true probability.
OddsCapo educational content · Illustrative prices, not current offers
The formula for decimal odds
Implied probability = 1 / decimal odds. Multiply by 100 for a percentage. Odds of 2.00 imply 50%, 1.50 imply about 66.7%, and 4.00 imply 25%. These conversions describe the price, not an independently verified chance of winning.
For a simple win-or-lose bet, the reciprocal of the odds is the break-even probability before any fees or taxes. Markets with refunds or split stakes need additional settlement outcomes in the calculation.
Bookmaker margin and overround explainedPayout is not the same as profit
With a stake of 100 at 2.20, a winning bet returns 220 including the original stake. Net profit is 120. A losing bet loses the stake. The example does not recommend a stake size.
Comparing 2.20 with 2.10 on the same bet means comparing 220 with 210 returned per 100 staked. Better odds improve the payout if you win, but do not make the selection more likely to win.
Why probabilities add up to more than 100%
For a complete mutually exclusive 1X2 market, add 1 / home odds, 1 / draw odds and 1 / away odds. Odds of 2.00, 3.50 and 4.00 total approximately 103.57%. The excess is the quoted overround.
Use prices from the same bookmaker and comparable time. Mixing the best prices from different bookmakers creates a different calculation. Overround is not the bookmaker’s guaranteed realised profit.
A simple margin adjustment
One estimate divides each implied probability by the total. For the example above, the home probability becomes 0.50 / 1.0357, approximately 48.3%. This proportional normalisation removes the excess under an assumption that it is distributed proportionally.
Bookmakers need not distribute margin proportionally, and other adjustment methods can give different estimates. Do not label a normalised probability as the true chance. Use the calculation to understand prices and compare markets, not to promise certainty.
Compare in a match
Choose a match and the same market, selection and line. Inspect the timestamps in its history and confirm the available price and rules at the bookmaker before betting.
Related concepts
Bookmaker margin and overround explainedValue betting: expected value without guaranteesClosing line value (CLV): calculation and limitationsSources and method
Definitions and settlement are supported by the educational material below. These sources are commercial operators; their marketing is not evidence of future profit. Worked calculations are our own.
18+. Gambling involves the risk of losing money. No guide, graph or calculation guarantees profit. Responsible gambling.