A price and a probability answer different questions. The price describes the return offered for a successful bet; a probability describes how likely an outcome is under a particular assessment. Converting one into the other is useful, but the conversion does not discover the true chance of a football result.
Start with the reciprocal of the price
The decimal-odds conversion is one divided by the price, as shown in Betfair's odds explanation. Multiply the result by 100 to express it as a percentage rather than a decimal.
In the hypothetical table below, each percentage is the break-even win rate for a simple win-or-lose bet at that price, assuming no commission, voids or other adjustments. It is not our forecast for any named fixture.
| Decimal price | Calculation | Break-even percentage |
|---|---|---|
| 2.00 | 1 ÷ 2.00 | 50% |
| 4.00 | 1 ÷ 4.00 | 25% |
| 10.00 | 1 ÷ 10.00 | 10% |
| 100.00 | 1 ÷ 100.00 | 1% |
For example, imagine 100 separate one-unit bets at 4.00 with exactly 25 winners. Those winners return 100 units in total against 100 units staked, so the example breaks even; nothing in the quote guarantees those 25 winners will occur.
Why a full market can exceed 100%
Consider an invented home-draw-away market priced at 2.00, 3.60 and 4.00. Their reciprocal percentages are 50%, about 27.78% and 25%, totalling about 102.78%; these cannot all be mutually exclusive true probabilities because their total exceeds 100%.
One proportional adjustment divides each reciprocal by that total. In this worked example, the adjusted figures become about 48.65%, 27.03% and 24.32%, which sum to 100%; they are constructed estimates, not evidence that the home side truly wins 48.65% of the time.
Our published methodology averages quoted decimal prices by outcome, converts the resulting consensus market to reciprocals, and normalises that market. Therefore, a page's market-implied estimate is not necessarily the reciprocal of the specific bookmaker price displayed beside it.
Combining chances needs an assumption
For independent events, multiply their probabilities to find the chance that all occur; independence means that learning one outcome does not change the probability of the other, as Penn State's probability lesson explains. Separate fixtures are not, by themselves, proof that the assumption is correct.
In our hypothetical example, three mutually independent selections have estimated chances of 60%, 50% and 40%. Multiplying 0.60 × 0.50 × 0.40 gives 0.12, or 12%, for all three; averaging them to 50% would answer a different question.
If the estimates or independence assumption are wrong, the combined figure inherits that problem. For linked outcomes within one match, use the conditional reasoning in our builder guide, not a product of standalone percentages.
Common interpretation mistakes
- Calling the reciprocal a forecast: 25% derived from 4.00 describes the price threshold, not a verified chance.
- Confusing percentage points with percentages: moving from 25% to 30% adds five percentage points, a 20% relative increase in this example.
- Reading a tiny percentage as zero: a displayed estimate below 0.1% is not impossible, but it is also not a precise claim of one win in exactly 1,000 attempts.
- Treating past frequency as a promise: a theoretical probability is not a schedule telling you which attempt must win.
Check which number you are reading
First identify whether a percentage is a price conversion, a model estimate or a historical success rate. Then look for its assumptions, timestamp and treatment of related selections before comparing it with the quoted odds.
The price and uncertainty lesson explains how the offered price and estimated chance interact. Keep both visible: one without the other cannot establish an estimated pricing advantage.