Odds to probability: decimal, fractional and American
Odds are a price, and every price implies a probability. Converting them lets you compare lines from different sources on one scale.
Decimal odds
Implied probability = 1 / odds. Odds of 2.50 give 1/2.50 = 40%. Odds of 1.50 give 66.7%.
Fractional odds
A fraction a/b converts to decimal as a/b + 1. So 3/2 is 2.50, the same 40%.
American odds
Positive odds: decimal = 1 + odds/100, so +150 is 2.50. Negative odds: decimal = 1 + 100/|odds|, so −200 is 1.50.
One caveat
The probability from the odds includes the bookmaker's margin, so the two sides of a market add up to more than 100%. To see the market's own estimate, remove the margin first.
Related
Odds converter →Bookmaker margin calculator →Over/under in basketball: how totals work →Bookmaker margin: what it is and how to calculate it →Line movement in basketball: what it means →Basketball totals betting: over/under, how to choose and check →ROI in betting: what it is and how to calculate it →Small leagues and small markets in basketball betting →Live basketball betting: how it works and what to watch →Basketball betting for beginners: where to start →
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