THE SPORTS ODDS DESK / EXPLAINED
Decimal odds to implied probability
To convert decimal sports odds to an implied probability, divide 100 by the decimal odds. Decimal odds of 2.00 imply 50%; 5.00 imply 20%. A larger price corresponds to a smaller implied probability.
Step-by-step example: odds of 1.40
100 ÷ 1.40 = 71.428571…%. Rounded to one decimal place, the implied probability is 71.4%. The complementary implied probability is approximately 28.6%. These percentages describe the price, not a forecast about a particular match.
Keep full precision during calculation and round only the displayed result. Rounding each leg before multiplying can introduce avoidable differences on a multi-selection ticket.
Common decimal odds and probabilities
| Decimal odds | Implied probability |
|---|---|
| 1.10 | 90.91% |
| 1.20 | 83.33% |
| 1.25 | 80.00% |
| 1.40 | 71.43% |
| 1.50 | 66.67% |
| 1.80 | 55.56% |
| 1.90 | 52.63% |
| 2.00 | 50.00% |
| 2.50 | 40.00% |
| 3.00 | 33.33% |
| 3.36 | 29.76% |
| 4.00 | 25.00% |
| 5.00 | 20.00% |
| 10.00 | 10.00% |
| 20.00 | 5.00% |
| 100.00 | 1.00% |
Convert a probability back into decimal odds
If you have a probability expressed as a percentage, divide 100 by that percentage. For example, 25% corresponds to decimal odds of 4.00; 40% corresponds to 2.50.
If using a decimal probability such as 0.25, use 1 ÷ 0.25 instead. Do not divide 100 by 0.25 and call the result decimal odds. The calculator itself takes odds, not a probability estimate.
Bookmaker margin: why implied probabilities can exceed 100%
Imagine a two-outcome market with no draw, where both mutually exclusive outcomes are priced at 1.90. Each price implies about 52.63%. Together they add up to approximately 105.26%, not 100%.
The excess above 100%, about 5.26 percentage points in this example, is called the overround. It is one reason the inverse of a bookmaker’s price should not be treated as the actual chance of an event. Overround is not a guarantee of a bookmaker’s realized profit.
A simple proportional normalization divides each implied probability by their sum, giving 50% and 50% in this symmetric example. That is a modeling assumption, not proof of true probabilities. You need prices for every exhaustive, mutually exclusive outcome to perform such a normalization; a single entered price does not provide enough information.
Decimal odds are not American or fractional odds
Enter a price such as 1.50, 2.00 or 5.00. The calculator does not accept American notation such as +150 or fractions such as 3/2. If your sportsbook offers a display preference, select decimal odds first.
Using the formula for several games
For a standard parlay, multiply the individual decimal odds before applying the inverse. If your ticket already provides the final combined price, enter it directly. Read the parlay probability guide for a worked three-leg example and the independence assumption.