The fair-odds formula
For decimal odds, fair odds = 1 divided by probability expressed as a decimal. A 50% probability corresponds to fair odds of 2.00, while a 60% probability corresponds to approximately 1.67.
- 40% probability = 2.50 fair odds.
- 50% probability = 2.00 fair odds.
- 55% probability = about 1.82 fair odds.
- 60% probability = about 1.67 fair odds.
- 70% probability = about 1.43 fair odds.
Compare fair odds with market odds
If your estimated fair price is 1.67 and a bookmaker offers 1.80, the market price is higher than your fair price. That may indicate positive value if your probability estimate is accurate.
If the bookmaker offers 1.55 instead, the price may be too short even though you still consider the outcome likely.
Fair odds depend on the quality of the estimate
The calculation is simple; estimating probability accurately is the difficult part. Poor probability estimates produce poor fair prices, so fair odds should be supported by disciplined analysis rather than intuition alone.
Responsible betting
Football probabilities are estimates, not guarantees. Past results do not ensure future performance. Never stake money you cannot afford to lose and use licensed operators where gambling is legal for you.
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