Implied Probability Calculator
Convert any price into the chance the bookmaker is pricing in — and strip the margin out to see the true numbers.
Implied Probability Calculator
Turn any price into the chance the bookmaker is pricing in. Add every outcome to strip the margin out.
| Outcome | Decimal | Implied | Without margin |
|---|---|---|---|
| Home | 2.10 | 47.62 % | 45.43 % |
| Draw | 3.40 | 29.41 % | 28.06 % |
| Away | 3.60 | 27.78 % | 26.50 % |
| Total | 104.81 % | 100.00 % | |
The raw probabilities add up to 104.81 %. The 4.81 % above 100 is the bookmaker's margin — removing it leaves the true chances in the last column.
The Formula
Decimal odds and probability are two ways of writing the same thing, so converting between them is a single division:
- Implied probability: P = 1 / O
- As a percentage: P % = (1 / O) × 100
- Normalised across a market: P_norm = (1 / Oᵢ) ÷ Σ (1 / Oⱼ)
The first two give the raw figure — the bookmaker's margin is still baked in. The third divides by the market total, which cancels the margin out and leaves probabilities that sum to exactly 100 %.
Odds to Probability Table
Common decimal prices and the chance each one implies:
| Decimal odds | Fractional | American | Implied probability |
|---|---|---|---|
| 1.20 | 1/5 | -500 | 83.33 % |
| 1.50 | 1/2 | -200 | 66.67 % |
| 1.80 | 4/5 | -125 | 55.56 % |
| 2.00 | 1/1 | +100 | 50.00 % |
| 2.50 | 3/2 | +150 | 40.00 % |
| 3.00 | 2/1 | +200 | 33.33 % |
| 4.00 | 3/1 | +300 | 25.00 % |
| 5.00 | 4/1 | +400 | 20.00 % |
| 10.00 | 9/1 | +900 | 10.00 % |
| 20.00 | 19/1 | +1900 | 5.00 % |
Why It Matters for Value Betting
Value betting means backing outcomes whose real chance is better than the price suggests. You cannot judge that from decimal odds directly — 2.35 against 2.50 means little at a glance — but 42.6 % against 40.0 % is immediately clear.
The workflow is always the same: convert the price to a probability, remove the margin, compare against your own estimate. If your estimate is higher, the bet has positive expected value. Remember that the raw figure always overstates the chance, so comparing against it rather than the normalised number will make bad bets look good.
The margin you are removing is worth measuring in its own right — our bookmaker margin calculator reports it as a percentage and also gives you the fair no-vig prices behind any market.
Frequently Asked Questions
What is implied probability?
It is the chance of an outcome as expressed by the odds. Decimal odds are simply an inverted probability, so dividing 1 by the price converts it back: odds of 4.00 imply a 25 % chance. It tells you what the bookmaker thinks — plus the commission it adds on top.
How do I remove the margin from a probability?
Add up the raw probabilities of every outcome in the market. The total will exceed 100 % — that surplus is the margin. Divide each raw probability by that total and the figures normalise back to 100 %. For odds of 2.10 / 3.40 / 3.60 the raw probabilities total 104.81 %, so the true chances are 45.43 %, 28.06 % and 26.50 %.
Is implied probability the real chance of the outcome?
No, for two reasons. It includes the bookmaker’s margin, and it reflects where the money has gone as much as the sporting merits — prices shorten on popular teams regardless of their true chances. Normalising removes the margin but not the second bias.
How does this help me find value?
Value exists when your own estimate of an outcome’s chance is higher than the probability implied by the price. If a price implies 25 % and you rate the chance at 30 %, the bet is +EV. Converting odds to percentages is what makes that comparison possible — percentages are far easier to judge than decimal prices.
Does it work with fractional and American odds?
Yes. Switch the format above the inputs and enter prices as 3/2 or +150 — they are converted to decimal internally, so the probabilities come out the same either way.
More Betting Tools
- Bookmaker Margin Calculator — overround, margin and fair no-vig odds.
- Odds Converter — decimal, fractional and American in one place.
- Accumulator Calculator — total odds and payout for a multi.
- Bookmaker reviews — who prices sharpest in Nigeria.