Prediction Market Betting Explained: Event Contracts

Prediction market betting is trading event contracts that settle at $1 if an outcome happens and $0 if it does not. The price in cents is the market's implied probability, so a contract trading at 60 cents means the market prices the event at roughly a 60% chance. Instead of a bookmaker setting odds and baking in a margin, buyers and sellers set the price on an open exchange, which is what makes platforms like Kalshi and Polymarket different from a sportsbook.

That difference is the whole reason bettors are paying attention. A prediction market price carries no built-in vig, so it can track closer to true probability than a sportsbook line, and a contract that fills at 55 cents is a cleaner read on a 55% event than odds you still have to devig by hand.

Try It: Prediction Market Converter

Every prediction market price maps cleanly onto the betting odds you already know. Enter a contract price below to see it as American, decimal, and fractional odds, or enter odds to find the equivalent contract price.

Watch what happens as you drag the price up: the higher the cents, the shorter the odds, because a more expensive contract implies a higher probability. This is the same math behind our Prediction Market Converter tool, and it is the first step in comparing any prediction market against a sportsbook.

What an Event Contract Is

An event contract is a simple Yes or No claim about a future event, priced between 1 cent and 99 cents. Buy the Yes side and you are betting the event happens; buy the No side and you are betting it does not. At settlement the winning side is worth $1.00 and the losing side is worth $0.00.

Here is how to read a contract priced at 60 cents:

• A Yes contract at 60 cents means the market implies a 60% chance the event happens.
• If the event happens, each Yes contract settles at $1.00, a profit of 40 cents per contract.
• If the event does not happen, the contract settles at $0.00 and you lose your 60 cents.
• The No side trades at 40 cents, because Yes and No prices add up to about $1.00.

In betting terms, buying Yes at 60 cents is the same as taking −150 American odds (1.67 decimal): you risk 60 to win 40. The price is the probability, which is why a prediction market is often easier to reason about than odds you have to convert first.

Price to Odds at a Glance

Why the Exchange Model Matters

A sportsbook is the house. It sets both sides of a market and builds in a margin, called the vig or juice, so the implied probabilities add up to more than 100%. On a typical −110 / −110 market the book is pricing two 50% outcomes at about 52.4% each, and that extra 4.8% is its edge no matter who wins.

A prediction market works the other way. It is an exchange where users trade contracts against each other, so the price is discovered by supply and demand rather than dictated by a bookmaker. There is no structural vig, only a small trading fee on most platforms. Because nobody is padding the number to protect a margin, the price can sit closer to the market's honest estimate of probability.

That is a claim worth testing rather than trusting, and we did. In a study of over 600 million MLB player prop line movements, our sharpest sportsbooks analysis found Kalshi to be one of the sharpest price sources of any book or exchange in the dataset, with prices that tracked true probability more closely than most traditional sportsbooks. Prediction markets are not automatically cheaper on every event, but on the whole their prices behave like a sharp reference line.

Kalshi vs Polymarket

Two platforms dominate the category, and they are built differently.

Kalshi is a federally regulated exchange. It is designated by the Commodity Futures Trading Commission (CFTC), which makes it legal in most US states, including many where sports betting is not. Contracts trade on an open order book, settlement is based on publicly verifiable outcomes, and the platform charges a small fee on trades rather than a bookmaker's margin. Price a Kalshi contract directly with our Kalshi odds converter.

Polymarket is the largest prediction market by volume. It runs on the Polygon blockchain, so trades settle transparently on-chain with no intermediary setting the price. Its US availability has changed over time and continues to evolve, so confirm the current rules for your state before trading. Convert its prices with our Polymarket odds converter.

Both price the same way, a contract from 1 to 99 cents with the two sides summing to about a dollar, so the skills carry over from one to the other. The practical differences are regulation, the menu of markets, and liquidity on any given event.

Finding Value Across Platforms

The reason to convert a prediction market price to odds is so you can compare it against a sportsbook and see which side is offering more than the outcome deserves. The workflow is short:

1. Convert the contract price to odds with the tool above, so you can line it up against a book.
2. Devig the sportsbook line to strip out its margin and recover its honest probability. Our devigging guide explains the math, and the devigging calculator does it for you.
3. Compare the two probabilities. If the prediction market implies 55% and the devigged sportsbook line implies 60%, the sportsbook is pricing the event as more likely, so its side may hold the value. If it runs the other way, the prediction market is the better read.

When two platforms disagree enough that betting both sides would lock in a gap, that is an arbitrage opportunity, and the SmartStake Arbitrage Finder scans dozens of books and exchanges to surface those crosses in real time. Arbitrage is not risk free: prices move between placements and limits get cut, so treat every gap as a candidate, not a sure thing.

The deeper skill underneath all of this is judging where the fair price sits, which is the same discipline behind positive expected value betting and closing line value. Prediction markets just give you a cleaner starting number to work from.

Following Sharp Prediction Market Money

The most interesting edge in prediction markets is not the price itself, it is watching who is trading. Because Polymarket settles on-chain, every position is public, and some wallets have a long record of pricing events better than the crowd.

SmartStake Insiders turns that into a feed. It surfaces Picks attributed to qualified wallets, traders whose historical positions passed an audit, so you can see where proven prediction market money is going before the wider market catches up. It is the same idea as our Smart Money signal on sportsbooks, applied to the transparent world of on-chain prediction markets. You can explore the feed inside the SmartStake app.

Following sharp money is a signal, not a promise. A wallet with a strong track record can still be wrong on any single contract, and past performance never guarantees a future result.

The Honest Risks

Prediction markets are cleaner than sportsbooks in some ways, but they are not free money.

• Liquidity varies. A thin market can move a lot on a single order, and you may not fill your whole size at the price you see.
• Fees still apply. Most platforms charge a trading fee, and on tight edges that fee can be the difference between a good bet and a bad one.
• Regulation is evolving. What is available to you depends on your state and platform, and the rules are still changing.
• The market can be wrong. A price is a consensus estimate, not a fact. Prediction markets have misjudged plenty of events, and any individual bet can lose.

Treat prediction market betting the way you would any other edge play: bankroll it responsibly, size your positions, and never stake money you cannot afford to lose.

Frequently Asked Questions

What is prediction market betting? Prediction market betting is trading event contracts that settle at $1 if an outcome happens and $0 if it does not. The price in cents equals the market's implied probability, so a contract at 60 cents means the market prices the event at roughly a 60% chance. You look for value by buying contracts you think are underpriced and holding or selling them.

How is a prediction market different from a sportsbook? A prediction market is an exchange where users trade contracts against each other, so the price is set by supply and demand rather than by a bookmaker. A sportsbook builds a margin, the vig, into its odds so the implied probabilities add up to more than 100%. Because a prediction market has no built-in vig, its prices can track closer to true probability.

Is prediction market betting legal in the United States? Kalshi is a federally regulated exchange designated by the CFTC and is available in most US states, including many where sports betting is not legal. Polymarket runs on-chain and its US availability has changed over time, so check the current rules for your state before trading.

Are Kalshi and Polymarket odds better than sportsbook odds? Prediction market prices often track closer to true probability than sportsbook odds because they carry no built-in vig, and a SmartStake study of MLB player props found Kalshi to be one of the sharpest sources of all. That does not make them cheaper on every event, so convert the price to odds and compare it with a devigged sportsbook line first.

How do I convert a prediction market price to betting odds? Divide 100 by the contract price in cents to get decimal odds, then convert to American or fractional from there. A 60 cent contract is 100 divided by 60, or 1.67 decimal odds, which is −150 in American odds. The Prediction Market Converter does this instantly in both directions.

What can you bet on in a prediction market? Prediction markets list contracts on elections, economic data, weather, crypto and stock prices, cultural events, and sports. Because they are exchanges rather than sportsbooks, they cover many outcomes traditional books rarely price.

Start Comparing Prices

Prediction markets give you something a sportsbook never will: a price that is the probability, set by an open exchange instead of a house protecting its margin. Convert a contract to odds, devig the book on the other side, and you can see exactly where the value sits.

Ready to put it to work? Try the Prediction Market Converter, then explore sharp on-chain money in the SmartStake app.