In the world of prediction markets, price discrepancies are money left on the table. Savvy traders are increasingly looking at Kalshi vs. Polymarket arbitrage opportunities, exploiting the spread between the regulated US exchange and the offshore crypto giant.
But is the "free money" actually real? Here is the breakdown of the math, the fees, and the tools you need to spot the arb.
Why the Price Difference Exists
Polymarket (crypto) and Kalshi (regulated) often have different odds for the exact same event. This happens for three reasons:
- User Base: Polymarket is dominated by crypto whales; Kalshi is dominated by US retail traders.
- Liquidity: Polymarket often has higher volume, leading to faster price discovery.
- Fees: This is the killer. You must account for fees on both sides to see if the arb is profitable.
The "Fees" Trap
Before you bet on both sides to lock in a profit, you need to run the numbers.
- Polymarket: No trading fees, but you pay gas fees (MATIC) and potentially a 2% deposit fee if you are on-ramping fiat via MoonPay.
- Kalshi: Charges trading fees on every contract. You can view their fee schedule here.
Tools to Spot the Arbitrage
You cannot eyeball this. You need automated tools that scan both order books in real-time.
1. Polymarket Whales (Twitter/X)
While not a dedicated arb tool, following accounts like Polymarket Whales can alert you to massive movements on one platform that haven't hit the other yet.
2. Insight Prediction
Insight Prediction offers paid tools and newsletters that often highlight these spreads. They analyze the "implied probability" difference between the two exchanges.
3. Build Your Own (Python)
If you are technical, the best edge is building a simple script. You can pull the Polymarket CLOB API and compare it against the Kalshi API.
The Verdict
Arbitrage between Kalshi and Polymarket is possible, but margins are thin. The best opportunities usually appear during high-volatility news events (like election nights or Fed rate announcements) where one market reacts seconds faster than the other.
Find more Arbitrage Tools in our Directory.