Favorite (negative)
Implied probability = −odds / (−odds + 100). Example: −150 → 150/250 = 60%.
Odds math · education
American odds → implied probability → fair price.
Sportsbooks post American prices. Models speak in probabilities. Bridging the two is the whole fair-odds workflow: convert the book, remove juice when comparing a market, and ask whether the model number is still better than the price you can actually bet.
The formulas
Two directions, one comparison.
Dog (positive)
Implied probability = 100 / (odds + 100). Example: +130 → 100/230 ≈ 43.5%.
Probability → fair American
If p ≥ 50%: fair = −(p / (1−p)) × 100. If p < 50%: fair = ((1−p) / p) × 100.
Use the free tool
Skip the mental math with the fair-odds calculator. Concept primer: fair odds explained.
Worked examples
Illustrative prices — not recommendations.
| Book price | Implied | Model win% | Fair American | Read |
|---|---|---|---|---|
| −120 | 54.5% | 58% | ≈ −138 | Model thinks the favorite is underpriced vs −120 |
| +155 | 39.2% | 36% | ≈ +178 | Book dog is shorter than model fair — pass unless you disagree |
| −105 / −115 two-way | ~51.2% / 53.5% | — | De-vig first | Sum of implied > 100% is the juice; compare model to no-vig fair |
Where it shows up
Soccer, CBB and documented picks.
On the board
- Soccer projections — fair 1X2 beside books
- CBB projections — spread and ML fair prices
- Closing line value — taken price vs close
FAQ
- Is implied probability “true” chance?
No — it is the book's price converted to percent, including juice.
- Why publish American prices on picks?
So the record grades the number you could actually bet.
Access
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