Free tool
Implied probability calculator
What a price says about the chance, and what a chance says the price should be.
Any format.
- Implied probability
- 29.4%
- what the price says, margin included
- Decimal
- 3.40
Your own estimate, as a percentage.
- Fair decimal price
- 3.33
- the price with no margin
- Fair fractional
- 7/3
Runs in your browser. Nothing you type is sent anywhere or stored.
From price to probability
A decimal price is a return per unit staked, so its reciprocal is the probability at which that return breaks even. 2.00 breaks even at 50%; 1.50 at 66.7%; 5.00 at 20%. That is the implied probability, and it is the bookmaker’s opinion of the chance with their margin folded in.
The margin is why the number is always a little high. If the true chance of an outcome were exactly what the price implies, every bet at that price would lose the margin on average. The bookmaker margin calculator shows how much.
From probability to price
The reverse is the useful direction. Estimate the chance yourself — from a model, from the statistics, from whatever you trust — and one divided by that estimate is your fair price. A price on offer above your fair price is a positive-expectation bet on your numbers; below it is not.
How much above matters. Probability estimates carry error, and a price 1% better than fair is inside that error for almost any method. This site does not advise a bet below a 4% edge, and even that threshold is a judgement rather than a law.
Questions
- What is implied probability?
- The chance of an outcome that a price corresponds to if the bookmaker took no margin: one divided by the decimal price. A price of 4.00 implies 25%.
- Why do the implied probabilities in a market add up to more than 100%?
- Because the prices include the bookmaker’s margin. A typical three-way football market adds up to about 104 to 108%. The excess is the overround, and dividing each implied probability by the total gives the fair probabilities.
- What is a fair price?
- The price at which a bet has zero expected value for a given probability: one divided by the probability. If you make an outcome 30% likely, its fair price is 3.33; anything longer is value for you, anything shorter is not.
- How does this site use implied probability?
- Every match page shows the model’s probability, its fair price, the best price we last captured and the probability that price implies, with the gap between them. A bet is advised only when the model’s probability beats the price by at least 4%.
The same numbers on real fixtures
Other free tools
- Odds converter
Decimal, fractional and American odds side by side, with the probability each implies.
- Bookmaker margin calculator
The overround built into a market, and the fair odds once it is removed.
- Expected value calculator
Whether a price beats your probability, and by how much per unit staked.
- Kelly criterion calculator
A stake sized to the edge, with the fraction and cap we use ourselves.
- Accumulator calculator
Combined odds, returns and the true chance of an accumulator landing.
- Poisson football calculator
Expected goals in, match result, totals, both teams to score and likely scores out.
A calculator turns your numbers into other numbers. It does not know whether your numbers are right, and no arithmetic makes an outcome certain. Never stake money you cannot afford to lose.