Prediction Market or Betting Exchange? Read the Price Both Ways
One price, two vocabularies. Here is how a cent price, a back and a lay line up, and what each venue's own text says.
A prediction market sells a contract that pays 1 dollar if an outcome happens, and its price in cents is the market's probability: 41 cents is 41%, or decimal odds of 2.439. A betting exchange such as Orbit Exchange matches backers and layers at decimal odds. On both you are matched with other users, and the site reads buying “No” as the lay side. They differ in who decides the result, how fees are taken and how you reach them. Below: the sums, a side-by-side table, and each venue's own words.
One price, read in odds
A price of 41 cents and a price of 2.439 are the same thing. One is quoted in cents on a dollar, the other in decimal odds.
Kalshi writes that each contract is worth 1 dollar if you are right. Polymarket writes that winning shares are redeemable for $1.00, and that every share is priced between $0.00 and $1.00. Kalshi describes the price as a probability from 0% (certain not to happen) to 100% (certain to happen). So the price in cents is also the chance in percent.
The two sides of a market add up to the dollar (a Yes at 41 cents and a No at 59). Kalshi's price page says it plainly: the combined investment of both users must equal $1.
To get decimal odds, divide 100 by the price in cents. 41 cents gives 2.439, 59 cents gives 1.695, 62 cents gives 1.613 and 28 cents gives 3.571. Type a price into the converter below. In the field called “Prediction market price (cents)” you get the decimal odds back; the odds converter holds the other formats and the margin check.
Odds converter
Convert a price between six formats, turn a probability or a prediction market price into odds, and measure the margin in a market. Everything is worked out in your browser and nothing is sent anywhere.
Convert one price
Choose the format you have, type the price and read the same price in every format. Type fractions as 5/2, 5-2 or 5:2, and give American odds their sign, such as +150 or -200.
Probability or market price to odds
A chance and a prediction market price say the same thing in different units. Fill in either box, or both: each one gives its own decimal odds.
A price of 40 cents on a market that pays 1 unit is a 40% implied chance.
Margin check
Type the decimal odds of every outcome in one market, taken from one source at one moment. Leave outcome 3 empty for a market with two outcomes.
Proportional method: each implied probability is divided by the booksum, so likelier outcomes lose more points. Other methods spread the margin differently.
A Yes at 41 cents
Say you buy a Yes at 41 cents. If you are right it pays 1 dollar, a profit of 59 cents on 41; if you are wrong you lose the 41. That is decimal odds of 2.439.
A No at 59 cents is the other side of the same line: it risks 59 to win 41, which on an exchange is a lay at 2.439 against a backer's stake of 41.
This is arithmetic on a made-up price. It does not say what any contract is worth.
Who you trade with, and how the price forms
Start with Kalshi. Its help centre writes: “On Kalshi, you are always trading against another member of the platform, not the exchange itself.” Kalshi's API documentation gives the book's rule of translation: a bid to buy Yes at X is the same thing as an offer to sell No at one dollar minus X. The help centre adds that there is “no inherent difference between buying a Yes contract and selling a No contract, or vice versa”.
Polymarket says the same of itself in other words: “You trade directly with other users, not against the house.” Its terms say prices are not set by Polymarket; they come from supply and demand in a central order book. The price you see is the midpoint between the bid and the ask, unless that gap is over $0.10, when the last traded price is used. Polymarket's own example is a 37% price sitting between a 34 cent bid and a 40 cent ask. That price is a display, not what you will pay. If you think a probability is too high, Polymarket's documented answer is to buy No.
Orbit Exchange’s own text says users place back and lay bets, “matching their bets with other users with opposing views”, and in a lay its betslip text reads: “In a lay bet, you'd risk an amount the backer would naturally win.”
Different words for the same position, on the site's reading: buy No, sell Yes, lay. I find the cents easier to read and the odds easier to compare. That is a taste, and your sums come out the same either way.
How a back and a lay work walks through the exchange side with a betslip.
Side by side
Six rows, two columns. Each cell is a short statement; none of them ranks one against the other.
| Point of comparison | Prediction market | Betting exchange |
|---|---|---|
| Price quoted as | Cents on a dollar | Decimal odds |
| Taking the other side | Buy No or sell Yes | Lay |
| Pays on a win | 1 dollar per contract | Stake times the odds |
| Fees | Polymarket: formula on price, takers only. Kalshi: fee on expected earnings | Commission on the net profit of a market; the rate comes with the route |
| Result decided by | Kalshi decides, by each contract's rules. Polymarket: UMA Optimistic Oracle | Official result of the governing body, unless market rules say otherwise |
| Leaving before the end | Sell your position to a willing buyer | Cash Out, which is not always available |
Take the fees row one venue at a time. Polymarket publishes a formula, fee = C × feeRate × p × (1 - p), where C is the number of shares and p the price. Its table lists a Sports rate of 0.05 for takers and 0 for makers, and it says makers are never charged. Say 100 shares at 41 cents with that taker rate: the formula returns 100 × 0.05 × 0.41 × 0.59 = 1.2095 dollars, and a maker pays nothing.
Kalshi writes that it makes money by charging a transaction fee on the expected earnings on the contract, and it sends the full fee schedule and the maths behind it to a document on its own site. Read that schedule there. On Orbit Exchange the interface says “A commission is charged on net profit from each market”, and commission on net profit has the sum and the rate each broker states.
On the result row, the Orbit rule reads that markets “will be settled on the official result of the relevant governing body”. Kalshi points to each contract's rules and source, and Polymarket's markets carry resolution rules too, which is why those rules are worth reading before a trade.
For leaving a position early, Polymarket writes that you can sell “at any time before the market resolves, provided there is a willing buyer”. Orbit's Cash Out page says it can be unavailable when liquidity is low.
What each venue says about a game that starts
A game that kicks off changes the order book. On sports markets Polymarket says “outstanding limit orders are automatically cancelled once the game begins”. It adds that if a game starts earlier than scheduled, orders may not be cleared in time, so it asks you to watch your own orders when the start time moves.
Orbit Exchange has its own version: unmatched bets are cancelled at the start unless you chose “At In-Play: Keep”. The page on back and lay bets mentions that option.
Kalshi's lifecycle text for a market past its close time reads “No new orders accepted. Awaiting determination.” The help centre says determination can take “anywhere from one hour to more than twelve hours” after the market closes.
Polymarket's route is different. A proposed result opens a challenge period of 2 hours. If someone disputes it, a debate period of 24 to 48 hours begins. Orbit's rules say markets are generally settled shortly after the end of the event in question.
Three descriptions, three routes. The page does not say which is faster, because no source compares them. Kalshi says the rules are in each contract's terms, and Polymarket's documentation says to read the resolution rules before trading. Do that first.
Side note: “market” does double duty in this page, a venue in one sentence and a single question in the next. Back to the point.
Sportmarket's prices carry their fee
Sportmarket's own help says prediction-market odds are not always directly comparable across the betslip. Check what a price includes before you compare it.
Reaching them through a broker
The matrix this site keeps lists Kalshi under BetInAsia (BLACK) and MadMarket (Edge), and Polymarket under BetInAsia (BLACK), MadMarket (Edge) and Sportmarket. MadMarket's Edge page says Polymarket and Kalshi are now available on Edge.
Sportmarket describes how they look once you are in. Its help says prediction markets appear like any other bookmaker on your account, with odds shown in decimal format alongside your other bookmakers, and fees built into the odds. For a dispute about a specific market outcome, it says to contact the platform directly.
Each platform states in its own documents who may not trade: the Member Agreement for Kalshi, the Terms of Use and the geographic-restriction documentation for Polymarket. Read them before you register. For Orbit Exchange, the brokers' own lists are laid out in each broker's own country list.
Which broker opens which place is a lookup, not a paragraph: which broker opens which place answers it for all sixteen venues.
Which fits which bet
Prediction market
A contract that pays 1 dollar.
Best for: a bettor who wants a contract that pays 1 and a way to sell before the end if there is a buyer.
Not ideal if: you need decimal odds on a screen of bookmaker prices.
Betting exchange
Back and lay at decimal odds.
Best for: a bettor who thinks in odds, back and lay, and net-profit commission.
Not ideal if: the event you want is not on the menu.
Via a broker
One account that opens several venues.
Best for: one account that reaches Orbit Exchange and the prediction platforms its broker opens.
Not ideal if: you want to deal with a platform directly.
What people ask next
Is a prediction market the same as a betting exchange?
The two work alike at the core: both match you with other users. They differ in the price (cents on a dollar against decimal odds), in how fees are taken, and in who decides the result.
What does a price of 41 cents mean?
It means the market puts the chance at 41%. A contract bought at 41 cents pays 1 dollar if you are right, which is decimal odds of 2.439: 100 divided by 41. The sum ignores fees.
Can you lay on a prediction market?
Buying No is the position this site reads as the lay side. Kalshi's API documentation writes: “A YES BID at price X is equivalent to a NO ASK at price ($1.00 - X)”. A No at 59 cents is the other side of a Yes at 41.
Who decides the result of a prediction market?
Kalshi says it determines the outcome from the rules and the source in each contract's terms. Polymarket's documentation says its prediction markets use the UMA Optimistic Oracle. On Orbit Exchange, markets settle on the official result of the governing body unless the market rules say otherwise.
Can I reach Kalshi and Polymarket through a broker?
Kalshi is on BetInAsia and MadMarket. Polymarket is on BetInAsia, MadMarket and Sportmarket. The lookup of which broker opens which venue shows the whole matrix.
Where to go from here
If several picks in one position is what you are after, the fantasy comparison sets an exchange bet beside a Kalshi combo. If the odds side is the one you want, the exchange guide is the start. Orbit Exchange itself is reached through a broker: the way into Orbit Exchange lays the routes out, and comparing the four brokers sets them side by side.