Enter the contract price in cents, how many contracts you intend to buy, and your own probability estimate. The calculator returns the implied probability in that price, the equivalent decimal odds, your profit if the contract settles Yes, and the expected value per contract. Contracts settle at $1.00 or nothing, which is what makes the price and the probability the same number.
How Contract Pricing Works
A prediction market contract pays $1.00 if the event happens and $0 if it does not. You buy at whatever the order book is asking, so a contract trading at 45c costs 45c and either returns a dollar or expires worthless. The payout is fixed and the price is the only variable.
Divide the price by 100 and you have the market’s probability. 45c means 45%. Convert that to decimal odds with 1 ÷ 0.45 = 2.222 and you can hold it up against a sportsbook quoting the same event, which is the comparison the Odds Converter handles when you are coming from the other direction.
A Worked Example
One Yes contract trading at 45c, settling at $1.00.
- Contract price: 45c.
- Implied probability: 45%.
- Equivalent decimal odds: 1 ÷ 0.45 = 2.222.
- Profit if it settles Yes: 55c on 45c risked, an ROI of +122%.
- 100 contracts: $45 to buy. Yes settles at $100 for a profit of $55, No settles at $0.
- Your estimate at 52%: EV per contract = 0.52 × $1.00 – 0.45 = +7c before fees.
That last line is the one that decides whether to trade. The market has priced 45%, you have priced 52%, and the seven cents is what that disagreement is worth on each contract while the payout stays flat at a dollar.
Reading the Output
Implied probability tells you the market’s number. Your estimate is the number you brought. Everything the calculator reports downstream is a restatement of the gap between them, seven points in the example above, priced in different units.
Decimal odds matter when you hold accounts on both sides. A 45c contract is 2.222, so a bookmaker showing 2.30 on the identical outcome pays more for the same risk and the trade belongs there instead. Run both through the Implied Probability Calculator when the two venues quote in formats you cannot compare at a glance.
Expected value scales in a straight line with size, and that is where the number quietly overstates itself. Seven cents becomes $7.00 across 100 contracts and $70.00 across 1,000, but only if the book holds at 45c for the full order.
Fees, Depth, and Who Set the Price
The +7c figure is a pre-fee number. Fee structures vary by venue: some charge on the trade, some take a percentage of profit at settlement, some build the cost into a wider spread and advertise nothing. Two cents of fee against seven cents of edge removes most of the trade, so read the schedule for the specific market before sizing anything.
Depth is the second drag. A screen showing 45c might hold a few hundred contracts at that level before the price steps up, and filling the rest at 46c and 47c lifts your average cost above the number your edge was calculated from. Enter the price you filled at rather than the one you saw.
Then there is the question of where 45c came from. On a liquid contract it came from people with money at stake, updating faster than you can. A seven-point disagreement is a trade worth making. A thirty-point disagreement usually means you have misread the settlement rules, and the input deserves a second look before the money goes down.
Where the Estimate Comes From
The arithmetic on this page takes a second. Producing the 52% is the part that decides whether you make money, and it is the part Gecko Edge was built for. The platform generates a win probability for football markets from Poisson goal models with a Dixon-Coles correction, blends in market and league priors, then runs the same expected value test across 130+ leagues. The Expected Value Calculator applies that test to a single bookmaker price if you want to work one market by hand.
Further Reading
- All betting calculators: the full library of 34 free tools
- Sentiment vs stats: navigating betting market trends with AI
- What does EV mean and how should you use it?
How do I convert a prediction market contract price into betting odds?
Divide the price in cents by 100 to get the implied probability, then divide 1 by that figure for decimal odds. A contract at 45c implies 45%, and 1 ÷ 0.45 = 2.222. Compare that with the sportsbook price on the same event, remembering that the bookmaker’s number carries margin while the contract price carries fees at settlement.
How do I calculate expected value on a prediction market contract?
Multiply your probability estimate by the $1.00 payout and subtract the contract price. Rating a 45c contract at 52% gives 0.52 × $1.00 – 0.45 = +7c per contract before fees. A negative result means the price sits above your own valuation, and the other side is the trade to consider.
Do prediction markets offer better prices than sportsbooks?
Sometimes. Exchange-style markets carry no built-in overround, so the quoted price reflects what participants will pay rather than a bookmaker’s margin. Against that, fees apply on trades or settlement and liquidity is thinner outside headline events. Compare the all-in cost on both venues for the specific market.
What fees do prediction markets charge?
Fee structures differ by venue and by contract. Some platforms charge a per-contract trading fee, some take a cut of profit at settlement, and some recover the cost through the spread. Check the current schedule for the market you are trading, then subtract it from your expected value before deciding whether the edge survives.