# Implied probability: turning odds into a percentage

> Implied probability is the chance built into betting odds. See the formulas for decimal and American odds, three worked examples and why a market adds to over 100%.

Source: https://reviewstandings.com/what-is-implied-probability/
Updated: 2026-11-13

Implied probability is the chance a betting price builds in. For decimal odds D it is 1 divided by D; for American odds +A it is 100 divided by A plus 100, and for -A it is A divided by A plus 100. So +100 implies 50%, +150 implies 40.0% and -200 implies 66.7%.

## The formulas

- Decimal odds D: probability = 1 / D.
- American plus number +A: probability = 100 / (A + 100).
- American minus number -A: probability = A / (A + 100).

Each result is a share, so multiply by 100 for a percentage.

The formula for a minus number divides the amount you must stake by that stake plus 100, which is why a bigger favourite gets a higher percentage.

A plus number works in reverse: the bigger the plus, the lower the percentage. Fractional odds a/b first convert to decimal as 1 + a/b.

**Bottom line:** every price can be read as a percentage, and the percentage includes the sportsbook's margin.

## Three worked examples

**Implied probability from odds · hypothetical prices · Example (not an offer)**

| American odds | Working | Decimal odds | Implied probability |
|---|---|---|---|
| +100 | 100 / 200 | 2.00 | 50.0% |
| +150 | 100 / 250 | 2.50 | 40.0% |
| -200 | 200 / 300 | 1.50 | 66.7% |

Check the second row with the decimal formula: 1 / 2.50 = 0.40, or 40.0%. The same result from two formulas is a quick test of your arithmetic. Try your own price on [the odds converter](https://reviewstandings.com/odds-converter/).

## Why a market adds to more than 100%

Add the implied probabilities of every outcome in a market. If the sum is 104.76%, as in a hypothetical -110/-110 market, the extra 4.76 points is the margin. See [vig and juice](https://reviewstandings.com/what-is-vig/) for that worked example.

The same logic applies to a [moneyline](https://reviewstandings.com/what-is-a-moneyline/). For several legs together, see [the parlay calculation](https://reviewstandings.com/parlay-payout-calculation/).

## How we checked

The formulas and examples are derived by us from the definitions of decimal and American odds. No sportsbook price is used. More: [bet types, odds and margins](https://reviewstandings.com/bets-odds-and-margins/).

19+ in Ontario and British Columbia; 18+ in Alberta, Manitoba and Québec. Gambling involves risk. Play responsibly.

## FAQ

**What is the formula for decimal odds?**

Implied probability is 1 divided by the decimal odds. Decimal odds of 2.50 give 1 / 2.50, which is 40.0%.

**What is the formula for American odds?**

For a plus number A, divide 100 by A plus 100. For a minus number A, divide A by A plus 100. So +150 gives 40.0% and -200 gives 66.7%.

**Why do the probabilities of a market add to more than 100%?**

The sportsbook builds its margin into the prices. The excess over 100% is the vig, also called overround.

**Does implied probability tell me the real chance of winning?**

No. It is the chance the price implies, including the margin. It is not a forecast, and we do not suggest a bet is better because its implied probability looks low.