How Do Prediction Markets Work: A Guide
From binary contracts and live pricing to order books, settlement mechanics, and how crowd wisdom turns trades into probability — here's exactly how prediction markets work.
Prediction markets are specialized platforms where individuals can buy and sell contracts based on the outcome of future events. Also known as betting markets, information markets, or decision markets, these markets harness the collective wisdom of participants to generate accurate forecasts on a wide range of topics, from elections and economic indicators to sports and pop culture. The general concept is simple: market prices reflect the aggregated information and beliefs of all traders about the likelihood of a particular outcome.
Most prediction markets in the United States operate under the oversight of the Commodity Futures Trading Commission (CFTC), which ensures that these markets remain fair and transparent. By allowing market participants to place bets on future events, prediction markets offer a unique way to aggregate information and produce predictions that often rival or outperform traditional opinion polls and expert analysis. The result is a dynamic environment where the price of a contract signals the market's best estimate of the probability that an event will occur.
How Prediction Markets Work
Short answer: You buy a contract that pays $1.00 if an event happens and $0.00 if it doesn't. These are known as binary contracts, since they have only two possible outcomes. The price you pay (between $0.01 and $0.99) equals the market's probability estimate. If you're right, you profit. If you're wrong, you lose your stake. Prediction markets are places where beliefs trade, with participants buying and selling based on their expectations of future events. You can also sell your position before the event settles.
That's it. Everything below explains the mechanics in detail.
New to prediction markets? Start with our full guide to prediction markets for beginners.
Event Contracts Explained
Every prediction market starts with a clearly defined question tied to a verifiable outcome.
| Contract Question | Source for Resolution | Settlement Date |
|---|---|---|
| "Will the Fed cut rates at the March FOMC meeting?" | Federal Reserve press release | Day of FOMC decision |
| "Will the Eagles win Super Bowl LXI?" | Official NFL results | Game day |
| "Will Bitcoin exceed $100K by Dec 31?" | CoinMarketCap closing price | December 31 |
| "Will there be a government shutdown before April 1?" | Congressional Budget Office | March 31 |
For each question, two contracts exist: Yes and No. Together, they always sum to $1.00. If Yes trades at $0.65, No automatically trades at $0.35. The asset prices of these contracts fluctuate based on market sentiment and the collective information available to traders.
On Kalshi (a CFTC-regulated exchange), every contract lists named "Source Agencies": the specific entities whose official data determines the outcome. This removes ambiguity: you know in advance exactly what determines whether you win or lose.
On Polymarket (a blockchain-based exchange), resolution is handled by the UMA oracle system: a decentralized process where outcomes are proposed, challenged, and verified through an on-chain dispute mechanism.
Market Pricing
Short answer: Price = probability. A $0.70 contract means the crowd thinks there's a 70% chance the event will happen. No oddsmaker sets the price; traders do. This price discovery process is driven by the market mechanism, which aggregates information from all participants to determine the most accurate probability estimate.
How Price Equals Probability
Contract prices range from $0.01 to $0.99. The price at any moment represents the market's collective probability estimate of the outcome. A contract at $0.40 means the market assigns a 40% chance to that event occurring.
Contract Price | Implied Probability | What It Means |
$0.10 | 10% | The market thinks the event is very unlikely |
$0.25 | 25% | Possible but improbable |
$0.50 | 50% | Coin flip — market is uncertain |
$0.75 | 75% | The market thinks the event is likely |
$0.95 | 95% | The market thinks the event is near-certain |
No complicated formula is needed — the price in cents is the probability in percent.
How Prices Move
Prices adjust in real time as traders buy and sell based on new information. When more traders buy Yes, the price rises (higher implied probability). When more sell, it falls. Every trade reflects someone putting real money behind their belief, which is why prediction market prices often react faster than polls, expert forecasts, or news outlets. These rapid price movements reflect the market's ongoing attempt to forecast an unknown future outcome as new information becomes available.
For example, during the June 2024 presidential debate, Biden's prediction market odds dropped within 15 minutes of the debate starting, a signal that traditional polls took nearly two weeks to confirm.
Converting to Betting Odds
For sports bettors coming from sportsbooks, here's how prediction market prices translate:
PM Price | Implied Prob. | American Odds | Decimal Odds |
$0.25 | 25% | +300 | 4.00 |
$0.40 | 40% | +150 | 2.50 |
$0.50 | 50% | +100 | 2.00 |
$0.65 | 65% | −186 | 1.54 |
$0.80 | 80% | −400 | 1.25 |
The key difference: prediction market prices have no built-in house edge (vig). Unlike traditional sports betting, where the sportsbook takes a cut, and both sides of a bet might imply 52.4% each (totaling 104.8%), prediction markets are more efficient for reflecting true probabilities. In a prediction market, Yes + No always equals exactly $1.00, or 100%.
Buying and Selling Contracts
Prediction markets use an order book, similar to a stock exchange, where buyers and sellers post their prices
| Order Type | How It Works | Best For | Fees |
|---|---|---|---|
| Quick (Market) Order | Instantly fills at the best available price on the order book | Speed — you want in now | Taker fees apply |
| Limit Order | You set the exact price you're willing to pay; the order sits on the book until someone matches it | Control — you want a specific price | No fees until filled (maker fees, which are lower) |
| Limit Sell Order | You set the price at which you're willing to sell contracts you already own | Exiting — you want to lock in profit at a target price | Maker fees |
On Kalshi, trading fees are calculated using this formula: fees = round up(0.07 × C × P × (1−P)), where C = number of contracts and P = price in dollars. There are no settlement fees, no processing fees, and no membership fees.
On Polymarket, there are no trading fees for makers or takers — the platform charges zero transaction fees. Users pay only minimal Polygon network gas fees (typically $0.02–$0.10 per transaction).
The Order Book
The order book shows all resting buy and sell orders at each price level. On Kalshi, you can see exactly how many contracts are available to buy or sell at each price:
Example: The order book shows 5,010 Yes contracts available to buy at $0.74 each, and 75,000 Yes contracts available to sell at $0.71 each. The $0.03 gap between the best buy ($0.74) and best sell ($0.71) is the bid-ask spread.
A tight spread (small gap) means the market is liquid; you can trade quickly without much price impact. A wide spread means fewer traders are active, and you may need to accept a worse price or wait for your limit order to fill.
How Selling Works
Unlike a sportsbook, where you're locked in until the event ends, prediction markets let you sell your position at any time. On Kalshi, selling works by buying the opposite side of your contract. Since Yes + No always equals $1.00, buying a No contract when you hold Yes is mathematically equivalent to closing your position; Kalshi automatically pairs them and credits you $1.00.
Settlement
How Settlement Works
| Step | Kalshi | Polymarket |
|---|---|---|
| 1. Event occurs | Source Agency data is published | Event outcome becomes known |
| 2. Resolution | Kalshi determines the outcome based on the filed contract terms | Anyone can propose an outcome by posting a $750 USDC bond |
| 3. Challenge period | None — Kalshi resolves centrally | 2-hour window; if disputed, the system resets and escalates |
| 4. Settlement | Winning contracts pay $1.00; losing contracts pay $0.00; no settlement fees | Winning tokens are redeemable for $1.00 USDC.e; losing tokens are worth $0.00 |
| 5. Payout | USD credited to your Kalshi account | USDC.e credited to your wallet |
Example Trade
Short answer: Buy a Yes contract at $0.40. If the event happens, you collect $1.00 and profit $0.60. If it doesn't, you lose your $0.40.
Step-by-Step Walkthrough
The market: "Will the Fed cut rates at the March 2026 FOMC meeting?"Current price: Yes = $0.40 | No = $0.60
You believe the Fed will cut rates, so you buy 100 Yes contracts at $0.40 each.
Detail | Value |
Contracts purchased | 100 Yes |
Price per contract | $0.40 |
Total cost | $40.00 |
Max profit (event happens) | $60.00 ($1.00 − $0.40 = $0.60 × 100) |
Max loss (event doesn't happen) | $40.00 (your full stake) |
Scenario A: You're Right ✅
The Fed cuts rates. Your 100 Yes contracts settle at $1.00 each. You receive $100.00 and profit $60.00 (minus any trading fees).
Scenario B: You're Wrong ❌
The Fed holds rates. Your 100 Yes contracts settle at $0.00. You lose your $40.00 stake.
Scenario C: You Sell Early 🔄
Two days after buying at $0.40, a dovish jobs report is released. The Yes price jumps to $0.65. You sell all 100 contracts at $0.65:
Detail | Value |
Bought at | $0.40 × 100 = $40.00 |
Sold at | $0.65 × 100 = $65.00 |
Profit | $25.00 (before fees) |
You locked in $25.00 profit without waiting for the FOMC meeting, exactly like selling a stock that has risen in value.
How Odds Reflect Probabilities
Short answer: The price IS the probability. No conversion needed. A $0.72 contract = 72% implied probability.
This direct relationship holds because of how contracts are structured:
- A Yes contract at $0.72 pays $1.00 if the event occurs → the market implies a 72% chance
- The corresponding No contract at $0.28 pays $1.00 if the event doesn't occur → the market implies a 28% chance
- Together: 72% + 28% = 100%
Why Prices Are Usually Accurate
Prediction market prices aggregate all available information, polling data, economic indicators, domain expertise, insider knowledge, historical patterns, into a single, continuously updating number. Research from the Federal Reserve Bank of San Francisco confirms that prediction market prices typically provide useful estimates of average beliefs about probability, with prices approximating the central tendency of all traders' beliefs.
Studies show that events priced at 70% tend to occur about 70% of the time, the markets are well-calibrated. This calibration exists because traders who are wrong lose money and leave the market, while traders who are right attract capital and gain influence over prices.
When Prices Can Be Misleading
Prices are less reliable when:
- Liquidity is thin: In small markets with few traders, a single large order can move the price significantly without reflecting genuine consensus
- Fees exist: Trading fees create a small gap between the contract price and the true implied probability. On Kalshi, the fee formula means a $0.50 contract (maximum fee point) costs slightly more than the raw probability suggests
- Risk aversion: Traders may demand a premium for holding risky positions, pushing prices slightly away from true probability estimates
Market Liquidity
Short answer: Liquidity measures how easily you can buy or sell contracts without moving the price. High-liquidity markets (presidential elections, Fed rates) have tight spreads and instant fills. Real money prediction markets typically attract more participants and higher liquidity than play money markets, which are often used for educational or regulatory reasons. Low-liquidity markets (niche events) may have wide spreads and slow fills.
What Determines Liquidity
Factor | High Liquidity | Low Liquidity |
Trader count | Thousands of active traders | Dozens of traders |
Bid-ask spread | $0.01–$0.03 | $0.05–$0.15+ |
Order book depth | Thousands of contracts at each price level | Tens of contracts |
Fill speed | Instant (market orders) | May wait hours or days |
Price impact | Minimal — large orders barely move the price | Significant — a $500 order can shift prices 5–10% |
Market Makers
Market makers are professional traders (or algorithms) that continuously post both buy and sell orders on the order book, earning the bid-ask spread in exchange for providing liquidity. They use dynamic pricing algorithms that widen spreads during volatile or illiquid conditions and tighten them during calm, high-volume periods.
On Polymarket, Automated Market Makers (AMMs) bootstrap liquidity for new markets before transitioning to a central limit order book (CLOB) as volume grows. On Kalshi, market-maker-supported liquidity ensures that even new markets have functional order books from launch.
Why Liquidity Matters for Traders
- Tighter spreads mean lower transaction costs: you lose less to the gap between buying and selling prices
- Deeper order books mean less slippage: your order fills closer to the quoted price
- Higher volume means more accurate prices: more traders = more information aggregated into the price
As a general rule, stick to markets with tight spreads ($0.01–$0.05) and visible order book depth of at least a few hundred contracts per price level. In thin markets, use limit orders rather than market orders to avoid overpaying.
Platform Overview
The prediction market ecosystem features a variety of platforms, each with its own strengths and areas of focus. Polymarket stands out as the world's largest prediction market, offering a decentralized environment where users can trade event contracts on everything from presidential elections to pop culture moments. Its use of blockchain technology and automated market makers ensures high liquidity and transparent trading activity.
Kalshi, a licensed derivatives exchange, specializes in event contracts tied to financial markets and economic indicators, providing market forecasts on topics like interest rates and inflation. PredictIt, meanwhile, is known for its focus on political events and election betting, making it a popular choice for those interested in current events and policy outcomes.
The Iowa Electronic Markets, operated by the University of Iowa since 1988, is one of the oldest and most respected platforms, with a long history of accurate predictions on political and economic events. Each of these platforms offers unique tools and features, such as real-time trading activity, detailed market forecasts, and a wide selection of event contracts, enabling users to make informed predictions and participate in the evolving world of predictive markets.
How Prediction Markets Work FAQs
What are prediction markets?
Prediction markets are platforms where participants buy and sell contracts based on the outcome of future events. These contracts pay out based on whether a specific event occurs, allowing the market price to reflect the collective probability of that event.
How do prediction markets work?
Participants buy binary contracts that pay $1 if the event happens and $0 if it doesn't. The price you pay represents the market's estimate of the event's probability. You can also sell contracts before the event settles to manage your position.
Are prediction markets legal?
In the United States, prediction markets are regulated by the Commodity Futures Trading Commission (CFTC). While federal regulators have become more relaxed over time, some platforms have faced legal challenges. State regulators may also have
What kinds of events can I bet on?
Prediction markets cover a wide range of topics, including elections, financial markets, sports, pop culture, and current events. The key is that the event has a clear, verifiable outcome.
Can I lose money in prediction markets?
Yes. Like any form of betting or trading, you can lose your entire stake if your prediction is incorrect. It's important to only bet money you can afford to lose.
How do prediction markets differ from traditional betting?
Prediction markets aggregate information from many participants, reflecting collective wisdom. Unlike traditional sportsbooks, prediction markets typically have no built-in house edge, making prices more efficient.
What is liquidity in prediction markets?
Liquidity refers to how easily you can buy or sell contracts without affecting the price. High liquidity means tighter spreads and more reliable prices, while low liquidity can lead to higher costs and price volatility.
What platforms offer prediction markets?
Popular platforms include Polymarket, Kalshi, PredictIt, and the Iowa Electronic Markets, each with different focuses and regulatory statuses.
James Guill is an experienced iGaming journalist with a diverse background spanning IT, poker, and online gambling media. With over 20 years in the industry, he’s covered a wide range of gaming topics and has been featured in outlets like USA Today and G4 TV.
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