Odds & Formats

Implied Probability

The probability of an outcome implied by the odds. Includes the bookmaker's margin (vig).

Also known as: implied odds, break-even probability

Definition

Implied probability converts odds into a percentage chance of winning. At -110 American (1.91 decimal), the implied probability is 52.4% — meaning you'd need to win more than 52.4% of the time to profit.

Critically, implied probabilities from bookmaker odds include vig. If you sum both sides of a two-way market, the total will exceed 100%. That overage is the bookmaker's margin.

True probability (what you think will actually happen) vs. implied probability (what the odds say) is the foundation of value betting.

Formula

From decimal: impliedProb = 1 / decimalOdds
From American (neg): impliedProb = |odds| / (|odds| + 100)
From American (pos): impliedProb = 100 / (odds + 100)

Worked Example

A -150/+130 market: favorite implied prob = 150/250 = 60.0%, underdog = 100/230 = 43.5%. Sum = 103.5%, so the vig is 3.5%.

Try It Yourself

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Related Terms

Vig

The bookmaker's built-in commission. The difference between true odds and what you're offered.

True Probability

The actual estimated likelihood of an outcome, with the bookmaker's margin removed.

Expected Value (EV)

The average profit or loss per bet if you made the same wager thousands of times. Positive EV means long-term profit.

Overround

The total implied probability exceeding 100% across all outcomes in a market — the bookmaker's total margin.