How to Calculate Implied Probability

For decimal odds, the basic formula is: implied probability = (1 / decimal odds) × 100.

• 1.50 odds = 66.7% implied probability.
• 1.80 odds = 55.6% implied probability.
• 2.00 odds = 50.0% implied probability.
• 2.50 odds = 40.0% implied probability.
• 3.00 odds = 33.3% implied probability.

If odds of 1.80 imply 55.6% and your model estimates 63%, the raw difference is about +7.4 percentage points. That is one way to express a potential value edge.

The model estimate should still be treated as uncertain. A probability is not a promise, and the accuracy of the estimate matters more than the size of the claimed edge.

In a complete market, the bookmaker's implied probabilities often total more than 100%. The amount above 100% is related to the bookmaker's margin. More advanced analysis can remove that margin before comparing probabilities.