Polymarket vs Kalshi: A Quantitative Comparison
A numbers-driven breakdown of fees, liquidity, contract types, and which platform gives you a better deal depending on what you trade.
Two platforms, different tradeoffs
Polymarket and Kalshi are the two dominant prediction markets, but they're built on fundamentally different models. Polymarket runs on Polygon (crypto rails), uses an open order book, and charges no trading fees. Kalshi is a CFTC-regulated exchange with a traditional fee structure. The right choice depends entirely on what you're trading and how much capital you're deploying.
Fee structures
Kalshi charges fees on winning trades only. The rate varies by contract type and volume, but a standard fee is around 7% of profit. Buy a contract at $0.40, it resolves Yes, and you pay $0.07 * $0.60 = $0.042 in fees on your $0.60 profit. Your net return drops from 150% to 139.5%.
Polymarket charges no trading fees. You pay gas costs on deposits and withdrawals (usually under $1), plus whatever spread exists on the order book. On a liquid market with a 1-cent spread, your implicit cost on that same $0.40 contract is roughly $0.01 — far less than Kalshi's fee.
Run both scenarios through the fee calculator and the difference is stark on high-confidence bets. A contract bought at $0.85 with a $0.15 max profit gets crushed by a 7% winner fee — you're losing over a cent on fifteen cents of upside.
Liquidity
Polymarket dominates on high-profile political and crypto markets. Presidential election markets regularly show six-figure liquidity within 2 cents of the midpoint. Kalshi's order books are thinner on comparable contracts but stronger on weather, economic data, and niche regulatory events.
The practical impact: placing a $5,000 order on a Polymarket presidential contract might move the price 0.5 cents. The same order on a thinner Kalshi market could move it 2-3 cents. Use the liquidity calculator to estimate slippage before you size up.
Contract types
Kalshi offers binary, range, and event contracts across categories Polymarket doesn't touch — Fed rate decisions, unemployment figures, temperature records. These are CFTC-regulated, which means US users can trade them legally and with tax clarity.
Polymarket covers politics, crypto, sports, culture, and pop events with more creative contract structures. Multi-outcome markets (who wins an award, which state flips) generate mispricings that binary-only platforms can't.
The bottom line
For high-volume trading on liquid political markets, Polymarket's zero-fee structure wins on raw EV. For regulated access, tax simplicity, and niche economic contracts, Kalshi is the only option. Most serious traders maintain accounts on both and route trades to whichever platform offers the better price after fees and slippage. For a deeper dive into fee impact, read how prediction market fees eat your edge. And if you're deciding between sportsbooks and prediction markets entirely, see sportsbooks vs prediction markets.