Fair odds are the price a bet would have if there were no sportsbook margin and the probability were exactly right. They’re the reverse of break-even: instead of turning a price into a percentage, you turn a percentage into a price.
The formula
Chance of 50% or more: −100 × chance ÷ (1 − chance)
Chance under 50%: +100 × (1 − chance) ÷ chance
| Estimated chance | Fair odds |
|---|---|
| 62% | −163 |
| 55% | −122 |
| 50% | +100 (even) |
| 45% | +122 |
| 40% | +150 |
Comparing fair odds with the posted price
Say your forecast for a pick is 62%, so the fair price is about −163. If the sportsbook offers −150, it’s paying a little more than your fair price. If it offers −180, it’s paying less. That’s the same comparison as estimate versus break-even, just written in odds instead of percentages.
- Posted price pays more than fair odds: the price is better than your estimate implies.
- Posted price pays less than fair odds: you’re paying extra for the same chance.
The catch: fair odds are only as good as the estimate
A fair price built on a wrong probability is still wrong. A few points of error in the estimate moves the fair price a lot near the extremes, which is why GammaLine shows the reasoning and the biggest uncertainty next to every number, and publishes how its models have performed. See the model checks.
Published by GammaLine · Updated September 29, 2026
More lessons: What’s a line, anyway? · What the price actually means · Why a likely pick can be a bad deal · How to read our forecast · How to read the odds: break-even and implied probability · Why a 60% pick still misses