Polymarket vs Kalshi: Quick Reference for Arbitrage Traders
Polymarket and Kalshi are the two dominant prediction market platforms in 2025, and price discrepancies between them regularly create real arbitrage opportunities worth capturing. When the same event trades at 62¢ on one platform and 67¢ on another, a trader who understands the mechanics of both can lock in near-risk-free profit — if they move fast and account for fees correctly.
Whether you're a casual trader looking to diversify or a systematic trader building automated strategies, this guide gives you everything you need to compare the two platforms, spot arbitrage windows, and execute profitably.
Platform Overview: What Makes Polymarket and Kalshi Different?
Before you can exploit price gaps, you need to understand why those gaps exist. Polymarket and Kalshi are fundamentally different products operating under different legal frameworks, which explains why their prices regularly diverge.
Polymarket is a decentralized prediction market built on the Polygon blockchain. It operates via smart contracts, uses USDC as its base currency, and is technically not available to US residents (though enforcement is limited). Because it's decentralized, anyone globally can participate, which creates deep, crypto-native liquidity on high-interest political and cultural events.
Kalshi is a regulated US exchange, licensed by the Commodity Futures Trading Commission (CFTC). It's a fully legal platform for US residents, trades in US dollars, and operates more like a traditional financial exchange. Kalshi launched federal event contracts and has aggressively expanded into sports, weather, economics, and political markets.
The key insight: different user bases + different regulatory environments = systematically different prices on the same event.
Side-by-Side Comparison Table
| Feature | Polymarket | Kalshi |
|---|---|---|
| Regulation | Unregulated (decentralized) | CFTC-regulated |
| US Residents | Technically restricted | Fully legal |
| Currency | USDC (crypto) | USD (fiat) |
| Blockchain | Polygon | None (centralized) |
| Maker Fees | 0% | 0% |
| Taker Fees | ~2% of winnings | 1–7% of winnings |
| Withdrawal | Crypto wallet | ACH / wire transfer |
| Typical Liquidity | $1M–$50M+ on top markets | $100K–$5M on top markets |
| Market Types | Political, crypto, sports, culture | Political, economic, sports, weather |
| API Access | Yes (public REST + WebSocket) | Yes (REST API) |
| Minimum Trade | ~$1 | $1 |
| Settlement Speed | Hours to days (oracle-based) | 1–3 business days |
This table alone is your starting point. Notice that Kalshi's taker fees are variable (ranging from 1% on competitive markets to 7% on niche ones), while Polymarket charges approximately 2% of winnings, not of your stake. That distinction matters enormously when calculating whether an apparent arbitrage gap is actually profitable.
Understanding Fees: The Make-or-Break Factor in Arbitrage
Most traders blow their first arbitrage attempt by misunderstanding fees. Here's the breakdown you actually need.
Polymarket Fee Structure
Polymarket charges no maker fee and a 2% fee on net winnings (not on the total payout). So if you buy YES at 60¢ and it resolves YES, your payout is 100¢ per share. The 2% fee applies to your 40¢ profit, costing you 0.8¢ per share. On a $10,000 position, that's $80 in fees — not trivial.
You also pay Polygon gas fees, which are typically under $0.10 per transaction, so effectively negligible compared to trading fees.
Kalshi Fee Structure
Kalshi's fee model is more complex. It charges a percentage of the amount risked (your potential loss, not your potential gain), and the rate varies by market:
- Tier 1 markets (high-liquidity): ~1% fee
- Tier 2 markets (mid-liquidity): ~3% fee
- Tier 3 markets (niche): up to 7% fee
Always check the specific market's fee before calculating your arbitrage spread. A 5¢ price gap can disappear entirely once fees are factored in on a Tier 3 Kalshi market.
For a deeper look at how slippage interacts with fees on these platforms, see this analysis of advanced slippage strategies for prediction markets — it includes backtested data that's directly applicable to cross-platform strategies.
How to Identify Arbitrage Opportunities Between Polymarket and Kalshi
Arbitrage in prediction markets exists when the same binary event (e.g., "Will the Fed cut rates in June?") trades at meaningfully different prices on two platforms after accounting for fees.
Step-by-Step: Finding a Valid Arb
Identify overlapping markets. Look for events covered on both Polymarket and Kalshi simultaneously. Political events (elections, Fed decisions, legislation) are the most common overlap.
Note the prices. Say Polymarket shows YES at 58¢ and Kalshi shows YES at 64¢. The raw gap is 6¢.
Calculate fees on both sides. On Polymarket you're buying YES (taker), paying ~2% of winnings. On Kalshi you're selling YES (or buying NO), paying Kalshi's applicable fee rate. Add them up.
Check if the gap exceeds total fees. If your combined fee burden is 4¢ and the gap is 6¢, you have a theoretical 2¢ edge per share.
Account for slippage. Large orders move prices. Use the order book depth to estimate how many shares you can buy before the price moves against you.
Assess execution risk. How quickly can you fund both accounts and place both sides? Any delay creates directional risk — the event outcome could shift before you complete both legs.
Execute simultaneously where possible. Use API-based execution or have both platforms open and funded in advance.
Track settlement timing. Polymarket may settle 24 hours before Kalshi on the same event. This creates a window of unhedged exposure.
For traders who want to automate this process, algorithmic cross-platform prediction arbitrage via API covers the technical implementation in detail.
The Most Common Arb Scenarios (With Real Examples)
Political Events
US election markets are the richest source of Polymarket vs Kalshi arbitrage. During the 2024 election cycle, YES contracts on several Senate race outcomes regularly showed 4–8¢ spreads between platforms, driven by Polymarket's international user base (more bullish on certain candidates) versus Kalshi's US-centric userbase.
Key insight: Polymarket often moves faster on breaking news because its crypto-native users are more reactive. Kalshi can lag by 15–30 minutes, creating a window.
Economic Data Events
Fed rate decisions, CPI prints, and jobs reports trade on both platforms. Because Kalshi is US-regulated, it attracts more institutional and financially sophisticated traders on economic events, which means its prices sometimes more accurately reflect consensus economist forecasts. Polymarket on the same events may reflect retail sentiment more than economic fundamentals — creating exploitable gaps.
Sports Markets
Both platforms now offer sports markets. Polymarket's sports markets tend to have lower liquidity than Kalshi's, making large arb trades harder to execute on Polymarket without moving the market. Stick to arbs where Polymarket's liquidity on that specific contract exceeds your intended position size by at least 5x.
If you're interested in sports prediction markets more broadly, this guide to AI-powered NFL season predictions offers useful context on how to evaluate sports-related market pricing.
Risks Every Prediction Market Arbitrageur Must Know
Arbitrage in prediction markets is not risk-free, despite what the math might suggest. Here are the real risks:
Settlement Risk
Polymarket and Kalshi may interpret the same event outcome differently. In 2023, a Polymarket political market settled YES while a comparable Kalshi market settled NO due to different resolution criteria. Always read both resolution sources before trading.
Liquidity Risk
On smaller markets, a 5,000-share order can move the market 3–5¢ before filling. What looked like a 6¢ arb becomes a 1–2¢ arb (or a loss) after market impact.
Capital Lock-Up Risk
Your capital is tied up on two platforms until the event settles. Opportunity cost matters — a 2% edge over 90 days is not the same as a 2% edge over 3 days.
Platform Risk
Polymarket's smart contracts have been audited, but decentralized systems carry smart contract risk. Kalshi carries regulatory risk — CFTC rule changes could affect market availability.
Traders looking to manage these risks systematically will benefit from reading about prediction market liquidity sourcing, which covers real-world examples of liquidity failure and how to anticipate it.
Using Technology to Scale Your Arbitrage Strategy
Manual arbitrage is slow and error-prone. Serious arbitrageurs use tools to:
- Monitor prices in real-time across both platforms via API
- Calculate net-of-fees spreads automatically
- Set alerts when gaps exceed a defined threshold
- Execute orders via API on both platforms near-simultaneously
Both Polymarket and Kalshi offer public APIs. Polymarket's API is REST and WebSocket-based, with order book data available without authentication. Kalshi's API requires an account and API key.
PredictEngine is purpose-built for this workflow — providing real-time multi-platform price monitoring, fee-adjusted spread calculations, and alert systems that flag valid arbitrage windows the moment they appear. Rather than watching two browser tabs and doing math manually, PredictEngine surfaces the opportunities algorithmically.
If you're interested in how AI enhances this kind of systematic trading, the AI-powered prediction market order book analysis article walks through a $10K real-money case study using algorithmic order book reading across platforms.
For even more advanced automated approaches, exploring AI agents for prediction markets is a logical next step — especially for traders who want to run continuous monitoring without manual oversight.
Practical Tips: Maximizing Your Polymarket vs Kalshi Edge
- Pre-fund both accounts. Arbitrage windows close in minutes. Have capital sitting idle on both platforms so you can execute immediately.
- Focus on markets with >$500K liquidity on both sides. Thin markets eat your edge via slippage.
- Trade before major announcements, not after. Post-announcement price movement is fast and crowds out arb.
- Use limit orders, not market orders. Market orders on prediction markets eat into your edge via spread.
- Keep a fee spreadsheet. Kalshi's variable fees mean you need to recalculate for every market. A simple spreadsheet with the formula built in saves you from costly mistakes.
- Track your ROI by event category. You'll likely find you have edge in some categories (e.g., economic data) and not others (e.g., entertainment). Focus capital there.
Frequently Asked Questions
Is arbitrage between Polymarket and Kalshi legal?
Yes, for most users. Kalshi is a CFTC-regulated exchange fully legal for US residents. Polymarket restricts US residents in its terms of service, so US traders should review their jurisdiction's rules. Non-US traders face no legal barrier to using Polymarket. Always consult a financial or legal advisor regarding your specific situation.
How big does a price gap need to be to be profitable?
As a general rule, you need a raw price gap of at least 5–8¢ to cover combined fees on both platforms and leave meaningful profit. On Tier 1 Kalshi markets with 1% fees and Polymarket's 2% winnings fee, a 4–5¢ gap can be sufficient. Always calculate net-of-fees spread before committing capital.
How fast do arbitrage windows close on Polymarket vs Kalshi?
Very fast — often 5 to 30 minutes on high-attention events. Automated bots and professional traders watch for these gaps constantly. On slower or niche markets, windows can stay open for hours or even days. Speed of execution is a decisive advantage.
Can I automate cross-platform arbitrage between Polymarket and Kalshi?
Yes. Both platforms offer public APIs that allow programmatic order placement and price monitoring. Tools like PredictEngine provide pre-built infrastructure for cross-platform monitoring and alerting, reducing the technical overhead significantly. For custom implementations, the algorithmic cross-platform arbitrage via API guide is the best starting point.
What events offer the most consistent arbitrage opportunities?
Federal Reserve decisions, major US political events, and economic data releases (CPI, jobs reports) are the most consistent sources of Polymarket vs Kalshi arbitrage. These events attract high volume on both platforms while maintaining different user bases and information sources, which creates persistent pricing divergence.
Does Polymarket or Kalshi have better liquidity?
Polymarket generally has deeper liquidity on political and crypto events, with top markets reaching $10M–$50M in volume. Kalshi's liquidity is growing rapidly following its sports and weather market expansion, but typically lags Polymarket on large political markets. For arbitrage purposes, always check liquidity on the specific contract you're trading — not platform averages.
Start Capturing Cross-Platform Prediction Market Edge
Polymarket and Kalshi will continue to price the same events differently — it's a structural feature of having two different platforms with different user bases, different fee models, and different regulatory environments. That structural difference is your opportunity.
The traders who profit consistently from this are not the ones who stumble onto a single lucky gap. They're the ones with pre-funded accounts, a clear fee calculation framework, and technology that surfaces opportunities faster than manual monitoring allows.
PredictEngine is built specifically for prediction market traders who want to operate at this level — with real-time price monitoring across platforms, fee-adjusted spread alerts, and the analytics infrastructure to turn systematic arbitrage from a theory into a repeatable strategy. Start your free trial today and see what you've been missing between the platforms.
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