Free tool
Implied Probability Calculator
Odds to percentage, and back · single price or whole market
Every price is a percentage in disguise. Type one in and read the other. Then add a second outcome to see how much of that percentage is fee.
The whole market
One price on its own cannot tell you how much fee is inside it. Add every outcome and the arithmetic gives itself away: the total comes out above 100%.
| Outcome | Implied | True |
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Implied is not the same as real
The percentage a single price implies is always too high, because the fee is inside it. The only way to get a figure that can be read as a real chance is to see the whole market at once. We publish that figure for every football match on the board today.
Free tier covers a fifth of each day’s matches, mixed across major and minor competitions. No card needed.
The conversion
Divide 1 by the decimal price. 2.00 becomes 50%, 4.00 becomes 25%, 1.25 becomes 80%. Going the other way, divide 100 by the percentage: 40% is a price of 2.50.
American odds take one extra step. A positive price p implies 100 ÷ (p + 100); +150 is 40%. A negative price implies -p ÷ (-p + 100); -200 is 66.7%.
Why the total gives it away
Exactly one outcome of a market happens, so the true probabilities must add to 100%. Convert the real prices and they never do. A two-way market at 1.91 each side gives 52.4% + 52.4% = 104.8%. A three-way football market usually lands between 104 and 108%.
The surplus is the fee, and it is spread through every one of those numbers. Removing it is what the no-vig calculator does; the method, and the honest limits of it, are on the maths page.
What the corrected number is, and is not
A de-vigged probability is the market’s opinion with the fee removed. It is a measurement of a price, not a forecast of a match, and not a recommendation. Markets are wrong regularly — a price at 80% still loses one time in five, and that is the number behaving correctly, not failing.
Questions
How do I calculate implied probability from decimal odds?
Divide 1 by the decimal odds and multiply by 100. A price of 2.50 implies 40 percent; a price of 1.25 implies 80 percent.
How do I calculate implied probability from American odds?
For a positive price p, implied probability is 100 divided by (p + 100): +150 gives 40 percent. For a negative price, it is the absolute value of p divided by (that value + 100): -200 gives 66.7 percent.
Why do implied probabilities add up to more than 100 percent?
Because the bookmaker's fee is built into every price. The surplus over 100 percent is the margin, known as the vig, juice or overround, and it is charged whether a bet wins or loses.
Is implied probability the same as the real chance?
No. Implied probability overstates the chance because the fee is inside it. Removing the fee across all outcomes gives a set of figures that add to exactly 100 and can be read as probabilities.