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Odds & Probability

Positive Expected Value

Also known as: +EV

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.

Related Odds & Probability Terms

Probability Distribution
A mathematical function that describes the likelihood of all possible outcomes in a betting event. Common distributions used in sports betting include the Poisson distribution for goals/points, the normal distribution for point spreads, and the binomial distribution for win/loss sequences. Understanding distributions helps bettors build predictive models.
American Odds (Moneyline Odds)
Odds format used primarily in the United States, expressed as positive or negative numbers. Positive odds (+150) show how much profit you win on a $100 bet. Negative odds (-200) show how much you need to bet to win $100 profit. +150 means a $100 bet wins $150 profit; -200 means you must bet $200 to win $100.
Odds Conversion
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.
Expected Value (EV)
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.
Fractional Odds
Traditional odds format used primarily in the UK and Ireland, expressed as a fraction (e.g., 5/2). The first number represents potential profit and the second represents the stake required. So 5/2 means you win $5 for every $2 staked. Fractional odds of 1/1 (evens) are equivalent to decimal odds of 2.00.
Overround (Book %)
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.
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