On this page (6 sections)
Content reviewed: 2026-10-13. Examples are hypothetical.
Cross-platform arbitrage pairs positions whose combined payout exceeds their total cost in every relevant settlement state. Finding different displayed prices is only the beginning. The positions must cover the same event, and both trades must actually fill.
Build the payoff table first
For an ordinary identical binary question, buying one Yes contract on one platform and one No contract on another should pay $1 in either outcome, assuming normal settlement and no counterparty failure. Rules determine whether that assumption holds.[1][2]
This hypothetical pair illustrates the arithmetic:
| Item | Cost per paired unit |
|---|---|
| Yes purchase | $0.46 |
| No purchase | $0.49 |
| Combined entry fees | $0.02 |
| Total | $0.97 |
If exactly one contract pays $1, net profit is three cents per matched pair. One hundred filled pairs cost $97 and return $100. The return on committed cost is 3 / 97, approximately 3.09%, before funding, withdrawal, tax or other costs. It is not a daily or annual return.
Check states that could break the pair
Compare the named source, deadline, time zone, definition of the event, cancellation rules and exceptional payouts. Add any plausible mismatch to the payoff table. If both positions can lose under different interpretations, the price gap is exposure to that disagreement rather than a locked payout.
Consider the case where one contract asks whether a bill is signed by a deadline and another asks whether it takes effect. The two outcomes can differ legitimately. A larger gap does not fix the mismatch.
Size for executable depth
Calculate both sides using the quantity you can actually obtain. Ten cheap contracts on one platform cannot hedge 100 contracts on the other. Record a maximum acceptable combined cost and abandon the trade when available prices cross it.
Order controls can limit individual fills, but a venue's fill-or-kill instruction does not coordinate an order at another venue.[3] Before submitting either side, decide how you would unwind an unmatched fill and what that unwind could cost. Avoid promising yourself that the missing side will become available later.
Reconcile completed exposure
Compare filled quantities, not submitted quantities, and account for residual orders. Keep each venue's records until both sides settle and funds are withdrawable. Include the duration capital stays committed when comparing opportunities.
The arbitrage calculator can help with costs, but it cannot establish that two contracts have identical rules or guarantee execution. For the platform-specific workflow, read Polymarket and Kalshi arbitrage.
Try the calculation
For a second worked scenario, load the paired payoff calculator. It uses 55-cent Yes and 38-cent No prices, one cent of entry fee per side and $95 of capital: 100 complementary pairs, with a $5 payoff after those fees if exactly one side pays $1.
References
- Polymarket Documentation. Resolution. Accessed October 13, 2026.
- Kalshi Help Center. Market Rules. March 17, 2026; accessed October 13, 2026.
- Polymarket Documentation. Place Orders. Accessed October 13, 2026.