Prediction markets / odds formats
Prediction market odds explained: convert a price to American odds
A prediction market prices a sports outcome in cents: 62¢ pays $1 if it happens. A sportsbook prices the same outcome as -163. Here is how to convert one into the other, and what spreads and fees do to the number.
What a prediction market price means
On a prediction market such as Kalshi or Polymarket, each outcome is a contract that pays $1 if it happens and nothing if it does not. The price is quoted in cents, from 1¢ to 99¢.
Because the payout is $1, the price reads directly as a probability. A Chiefs contract at 62¢ means the market rates the Chiefs at about 62% to win. A sportsbook shows the same view as American odds, decimal odds or a fraction. Converting between them is a few lines of arithmetic.
There are two prices on each side: the bid, what buyers offer, and the ask, what sellers want. If you want to buy now, the ask is your price, so that is the number to convert.
Convert a prediction market price to American odds
Start with the probability: p = price in cents / 100. Then pick the formula by which side of 50¢ the price is on.
Worked example: 62¢
p = 62 / 100 = 0.62, above 0.5, so this is a favorite.-100 × 0.62 / 0.38 = -163.16, which rounds to -163.- Decimal odds:
1 / 0.62 = 1.61.
Check it by payout. You pay 62¢ to collect $1, a gain of 38¢ on 62¢: $61.29 per $100. At -163, $100 wins $61.35. The few cents of difference come from rounding the odds to a whole number.
The other side: 38¢
The opposing contract at 38¢ is +100 × 0.62 / 0.38 = +163.16, so +163, with decimal odds of 2.63. A $100 stake wins $163.
Going back: American odds to cents
The odds converter and implied probability calculator do these conversions in the browser.
Prediction market price to American odds: conversion table
| Contract price | Implied probability | American odds | Decimal odds |
|---|---|---|---|
| 10¢ | 10% | +900 | 10.00 |
| 25¢ | 25% | +300 | 4.00 |
| 40¢ | 40% | +150 | 2.50 |
| 50¢ | 50% | +100 | 2.00 |
| 62¢ | 62% | -163 | 1.61 |
| 75¢ | 75% | -300 | 1.33 |
| 90¢ | 90% | -900 | 1.11 |
Vig, spreads and fees: prediction markets vs sportsbooks
A sportsbook builds its margin into the odds. The classic NFL spread is -110 on both sides. Each side implies 52.38%, so the pair adds to 104.76%. The 4.76% above 100% is the vig.
On a prediction market nobody sets a margin. What you pay above a fair price comes from two places:
- The spread. If the Yes ask is 62¢ and the No ask is 40¢, buying both sides costs 102¢ for a $1 payout. That 2¢ does the job vig does at a sportsbook, and it narrows or widens with the orders on the book.
- Fees. Some prediction markets charge a trading fee per contract, and each one sets and changes its own fee schedule. Add the fee to the price before you convert. With a 1¢ fee, a 62¢ contract really costs 63¢, which is
-170instead of-163.
So to compare a prediction market with a sportsbook fairly, convert the ask plus any fee into odds, then compare the same side of the same market. To compare margins, add both sides: implied probabilities for the sportsbook, asks for the prediction market. To strip the margin out and get a fair price, see CLV and +EV explained or the no-vig calculator. Through the API, fees=taker adds the price after a venue's published fee and devig=true adds the fair probability: see devig and exchange fees.
Size: limits vs resting depth
The amount you can bet also means something different. A sportsbook posts a limit, the most it will take on a market. A prediction market or exchange shows resting depth, the money sitting at the best price right now. Buy more than that and the rest fills at a worse price.
A tool that compares the two should never treat these as the same number. In the OddsLink API each price's size carries its kind: posted_limit for a sportsbook, resting_depth for an exchange or prediction market.
Polymarket, Kalshi and sportsbook odds in one shape
OddsLink carries Fanatics Markets, Kalshi and Polymarket as prediction markets, next to the exchanges and sportsbooks: 46 books on one fixture id. A prediction market price arrives in the same price field as a sportsbook price, in American or decimal odds as you ask, so your code reads Kalshi and DraftKings the same way. For Kalshi and Polymarket the price is the best ask converted to odds, so add any trading fee yourself.
That makes prediction market bots and cross-market odds screens a single request: ask for a fixture and read every book's price for each side. See the Kalshi odds API and Polymarket odds API pages for a real response, or the Python odds scanner guide to compare prices across books.
Questions
How do you convert a prediction market price to American odds?
Divide the price in cents by 100 to get the probability p. If p is above 0.5, American odds are -100 × p / (1 - p). If p is below 0.5, they are +100 × (1 - p) / p. At exactly 50¢ the odds are even money, +100.
What is 62 cents in American odds?
A 62¢ contract converts to -163 in American odds, 1.61 in decimal odds, and a 62% implied probability.
Is a prediction market price the same as a probability?
It is the market's implied probability at that moment: a 62¢ Yes contract pays $1, so the price says the market rates Yes at about 62%. The price you can buy at (the ask) sits a little above the middle of the market, and fees come on top.
Do prediction markets have vig?
Not as a built-in margin like a sportsbook. The cost comes from the spread between the best bid and best ask, plus any trading fee the market charges. Adding the Yes ask and the No ask shows the spread: 62¢ plus 40¢ is 102¢ for a $1 payout.
Which prediction markets does OddsLink carry?
Fanatics Markets, Kalshi and Polymarket, next to the exchanges and sportsbooks: 46 books in one JSON shape. See the Kalshi odds API and Polymarket odds API pages.
Can I compare Polymarket and Kalshi odds with sportsbook odds?
Yes. Convert both to implied probability or the same odds format, then compare the same side of the same market. OddsLink returns prediction market prices as American or decimal odds in the same fields as a sportsbook price, so the comparison needs no conversion code.
Prediction markets and sportsbooks in one response.
Fanatics Markets, Kalshi and Polymarket arrive as odds in the same fields as every sportsbook. Start on the Free plan with all 46 books.
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