Negative Expected Value

The process of converting odds between decimal, fractional, and American formats. Decimal to fractional: subtract 1, then simplify (2.50 = 3/2). Decimal to American: if odds >= 2.00, American = (Decimal - 1) x 100; if odds < 2.00, American = -100 / (Decimal - 1). Conversion is essential for comparing odds across different platforms.

Odds that have been adjusted to remove the bookmaker's margin (vig/juice), representing a fairer assessment of the true probabilities. To calculate no-vig odds, divide each outcome's implied probability by the total overround. No-vig lines are useful for identifying which side of a market has more value.

The actual likelihood of an outcome occurring, independent of the bookmaker's margin. True probability cannot be known with certainty, but it can be estimated through statistical models, historical data, and analysis. When your estimated true probability exceeds the implied probability, you have found a value bet.

A bet where the expected return is positive, meaning it will be profitable in the long run if placed repeatedly. A +EV bet occurs when the odds offered are higher than the true probability warrants. For example, getting odds of 3.00 on an outcome with a 40% chance of occurring. Professional bettors exclusively seek +EV opportunities.

The sum of the implied probabilities of all outcomes in a betting market, expressed as a percentage. A fair market totals exactly 100%, but bookmakers add an overround (e.g., 105%) to guarantee a profit margin. Formula: Overround = (1/Odds1 + 1/Odds2 + ... + 1/OddsN) x 100. Lower overrounds indicate better value for bettors.

The average amount a bettor can expect to win or lose per bet if the same bet were placed many times. Formula: EV = (Probability of Winning x Profit) - (Probability of Losing x Stake). A positive EV (+EV) indicates a profitable bet over the long term. EV is the single most important concept in professional betting.