Polymarket arbitrage explained
Arbitrage means buying every outcome for less than the guaranteed payout. It exists on Polymarket mostly in multi-outcome markets and between platforms, but fees, execution and rule differences eat most of it.
Three kinds of arbitrage
1. YES + NO under $1
In a binary market, if you can buy YES and NO for a combined price below $1 after fees, you lock in a profit. Market makers close these gaps within seconds, so they are rare for humans.
2. Multi-outcome markets
In markets with many candidates, the YES prices of all outcomes should add up to about $1. If they add up to noticeably less, buying every YES can lock in a profit; if more, buying every NO can.
3. Cross-platform
The same event can trade at different prices on Polymarket and Kalshi. The catch: different rules, different settlement sources and different timing. A “risk-free” trade becomes a bet if the two contracts resolve differently.
Check before you act
- Fees on every leg (use the arbitrage calculator).
- Liquidity at your size, not just the top-of-book price.
- Identical resolution wording and sources.
- How long the money is locked and what it costs to move it.
- Whether you are even allowed to use both platforms where you live.
Ready to try it? Check it is available where you live, then open Polymarket.
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