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Among the biggest prediction markets in the US, Kalshi is the largest by trading volume, and Polymarket US is second. According to DeFi Rate’s tracker, Kalshi handled about 76% of the tracked volume across nine venues in the 30 days leading up to October 25, 2026, with each contract counted at its $1 face value. Liquidity means how easily you can buy or sell a contract near the quoted price.
Liquidity shows up in trading volume, order book depth, and the bid-ask spread. Five of the six venues listed below are registered with the CFTC as either exchanges or intermediaries. PredictIt operates under CFTC staff no-action relief.
What Makes a Prediction Market Liquid
To find out which prediction market is most liquid, consider three numbers together. No single measure gives the full picture. Here’s how prediction market liquidity works, in the order a trader encounters it.
Trading Volume
Prediction market volume is the total value of contracts traded. Different trackers measure this in various ways, which affects the numbers. DeFi Rate counts each contract at its $1 face value, which is higher than the actual money traders paid.
Kalshi is a clear example of this gap. In the 30 days leading up to October 25, 2026, DeFi Rate counted $90.3 billion in Kalshi contracts, while only $20.4 billion was actually paid. Every trading volume figure on this page includes its tracker and the period it covers.
Order Book Depth
The order book shows all current buy and sell orders in a market. When there are many orders close to the current price, the book is considered deep. This means a large order can be filled near the price you see.
Polymarket’s documentation says its order book has no size limit, but placing a large order can still move the price significantly. This is why order book depth becomes more important as your order size increases.
The Bid-Ask Spread
The spread is the gap between the highest bid and the lowest ask. A smaller spread means the market is more liquid. Polymarket displays the midpoint between the bid and ask as the price, or uses the last trade price if the spread is wider than $0.10.
The midpoint is not always what you pay. For example, if the bid is 34 cents and the ask is 40 cents, the market shows 37 cents, but you still pay 40 cents to buy.
Why Liquidity Differs From Market to Market
Liquidity varies from market to market. Even if a venue has high total volume, smaller events can still have thin markets, wide spreads, and few resting orders. For example, a popular football game and a niche weather contract on the same venue may trade very differently.
Position limits also restrict how much you can trade. For example, PredictIt limits each trader to $3,500 per contract.
How We Rank the Most Liquid Prediction Markets
These are the criteria and weights behind the list of the largest prediction markets.
Trading volume|35
Order book depth and spread|30
Market range|15
Regulatory status|10
Fees|10
Trading volume is the main factor because it’s the only liquidity measure published for the largest venues. Order book depth and spread show how close a typical order fills to the quoted price. Market range, regulatory status, and fees are taken into account as well.
The largest prediction market by volume does not automatically come first. The order is calculated from all five criteria, and nobody moves a venue by hand. You can read how each score is built in our review methodology.
Biggest Prediction Markets Ranked by Liquidity
Each tile displays the most recent tracked volume, along with the tracker and the month. The largest prediction market by volume might not be at the top of the list.
Where Prediction Markets Are Legal
Federal Regulation by the CFTC
The Commodity Futures Trading Commission regulates prediction markets at the federal level. Kalshi (KalshiEX LLC), Polymarket US (QCX LLC), Crypto.com (Crypto.com Derivatives North America) and ForecastEx (ForecastEx LLC) are CFTC-designated contract markets. Robinhood Derivatives, LLC is a CFTC-regulated intermediary and NFA member that routes orders to exchanges.
PredictIt operates under CFTC staff no-action relief, in Letter 14-130 as amended by Letter 25-20 in July 2025.
State Court Actions
Some states have pushed back. On September 25, 2026, the Sixth Circuit ruled that Ohio and Tennessee can enforce their gambling laws against Kalshi’s sports contracts. A Michigan court has also blocked them in that state.
Other appeals courts have split on the question, and a petition is pending at the Supreme Court.
Availability can differ by state and by market category. Each venue lists its own restrictions.
Age Rules
Kalshi requires users to be 18 or older. Interactive Brokers offers event contracts to clients 21 and older.
Trading Risks and Responsible Play
A binary contract settles at $1 or $0. You can lose the full amount you paid for it. In a thin market, it can also be hard to sell before settlement at a fair price.
Set a budget before you trade and stick to it. Use the limit tools offered by each venue, and take a break if trading no longer feels like a choice. Our responsible gambling resources list where to find help.
Compare the two largest venues head to head, or see how liquidity looks in the market categories traders use most.
Venue volume figures come from DeFi Rate’s prediction market volume tracker, checked on October 27, 2026. The tracker counts contracts at $1 face value. Quarterly figures come from CoinGecko’s 2026 Q2 Crypto Industry Report, and Robinhood’s figure comes from its Q2 2026 earnings release filed with the SEC. Registrations were checked against CFTC records, and pricing and age rules against each venue’s own documentation, on the same date.
Methodology: our review methodology
