Odds Calculator

The Odds Calculator compares favorable to unfavorable outcomes: Odds = P(event) / P(not event). Probability is P(event) = favorable / total outcomes. For example, if probability = 0.25, then odds = 0.25/0.75 = 1:3.

From probability to odds: Odds = p/(1-p). From odds to probability: p = odds/(1+odds). For example, 3:1 odds means odds = 3, so probability = 3/(1+3) = 0.75 or 75%. This conversion is essential for interpreting betting odds.

Distinguish event odds from payout odds. Event odds of 3:1 in favor correspond to probability 3/(3+1) = 75%. Fractional betting odds of 3/1 describe a profit of 3 per unit staked and imply 25% probability before bookmaker margin; the equivalent decimal payout odds are 4.0. A percentage is a probability, not an odds ratio.

Betting odds indicate both probability and potential payout. Higher odds mean lower probability but higher payout. For decimal odds, multiply your bet by the odds for total return. Understanding implied probability helps identify value bets where your assessment differs from bookmaker odds.

Odds ratio compares odds between two groups: OR = (odds in group 1)/(odds in group 2). OR = 1 means equal odds, OR > 1 means higher odds in group 1, OR < 1 means lower odds. Commonly used in medical research and case-control studies.

Combine probabilities first, then convert the result to odds p/(1-p). For independent events, multiply probabilities for both to occur; for mutually exclusive events, add probabilities for either to occur. Do not multiply or add event odds directly. Two independent events each with probability 1/2 have joint probability 1/4 and odds 1:3.