What is implied probability?
Implied probability is the likelihood an outcome seems to reflect, based on the odds offered. It converts a price into a percentage that's easier to compare across different formats — American odds, decimal odds, or prediction-market share prices.
Prediction markets like Polymarket express prices as a decimal between 0 and 1 (e.g. 0.35 = 35% implied probability). Sportsbooks typically show American odds (e.g. −186) or decimal odds (e.g. 1.54). Converting all of them to a common probability scale is the first step to comparing them honestly.
American odds
American odds are the standard in US sportsbooks. Positive odds show how much you win on a $100 bet; negative odds show how much you need to bet to win $100.
| Odds | Implied Probability | Formula |
|---|---|---|
| +150 | 60.0% | 100 / (150 + 100) = 40% |
| -200 | 66.7% | 200 / (200 + 100) = 66.7% |
| +100 | 50.0% | 100 / (100 + 100) = 50% |
| +300 | 25.0% | 100 / (300 + 100) = 25% |
| -500 | 83.3% | 500 / (500 + 100) = 83.3% |
Positive odds: probability = 100 / (odds + 100)
Decimal odds
Common in Europe and Canada. The payout multiplier including your stake. A 2.00 decimal odds on a fair coin flip means a $100 bet returns $200 total ($100 profit + $100 stake back).
| Decimal Odds | Implied Probability | Formula |
|---|---|---|
| 2.50 | 40.0% | 1 / 2.50 = 40% |
| 1.91 | 52.4% | 1 / 1.91 ≈ 52.4% |
| 3.00 | 33.3% | 1 / 3.00 = 33.3% |
| 1.50 | 66.7% | 1 / 1.50 = 66.7% |
Prediction-market share prices
Polymarket and similar prediction markets price outcomes as shares between 0 and 1. A yes share trading at $0.65 means you pay $0.65 now and receive $1.00 if the outcome resolves YES — the share price directly represents the implied probability of that outcome.
No conversion needed: on Polymarket, the share price is the implied probability. 0.65 on Polymarket ≈ 65% implied probability of YES resolving.
Why implied probability alone is not enough
Even when two markets agree on implied probability, the effective probability you can act on may differ. These are the main reasons:
- On-chain fees: Polymarket charges a taker fee (~1% of notional on outrights) that slightly reduces your effective payout.
- Bid-ask spread: Prediction-market order books have a spread. Buying at the ask price is more expensive than the mid-price suggests.
- Sportsbook vig: Traditional sportsbooks embed a margin in their odds. The no-vig probability removes this, but you still need to know how to do that calculation.
- Settlement differences:A 90-minute match result and a “to qualify” market are not the same event — identical probabilities can still mean different things.
Use the calculator to convert between formats and see the no-vig probability side by side with prediction-market prices.
How to use this
When you look at a market on Kickoff Markets, the implied probability columns let you compare across formats without doing the math yourself. The score breakdown goes further — it shows which price differences survive after accounting for fees, spread, and liquidity.
Implied probability is a starting point, not a conclusion. The dashboard exists to show you where to look and what to question.