Prediction Market Arbitrage Calculator
Compare two opposite-side prices from platforms like Polymarket and Kalshi. See whether the combined cost may leave room for a cross-platform edge, then double-check liquidity, fills, and market rules before acting.
Explain It Like I'm 5
Two boxes, one prize
Imagine two boxes and exactly one box will have a $1 prize inside. If buying both boxes costs less than $1 total, the leftover gap can be your potential profit before fees, slippage, and execution problems.
Check A Two-Platform Setup
Use the buy price for one outcome on Platform 1 and the buy price for the opposite outcome on Platform 2. This calculator assumes both contracts pay $1 if they win. Example: one leg could be Kalshi YES and the other could be Polymarket NO on the same event.
Tip: label each side with both platform and outcome, such as "Kalshi YES" and "Polymarket NO".
Enter how many matched $1 shares you want to test on each side. Example: 100 means 100 shares on the first leg and 100 opposite shares on the second leg.
Estimated costs (optional)
Use percentage fees for each platform and optional fixed dollar costs for gas, withdrawals, bridging, or anything else you expect to pay for the whole setup.
Important
Both prices must refer to the same event, the opposite outcome pair, the same settlement wording, and the same $1 payout structure. A price difference alone is not enough. If you are comparing the same side on both platforms, that is price shopping, not arbitrage.
Run A Manual Check
Add the price from each platform to see the combined cost, your potential edge, and the quick checklist you should review before placing both orders.
How Prediction Market Arbitrage Works
This page uses the simplest version: buy opposite outcomes of the same event on two different platforms. If the total cost of covering both outcomes is less than the $1 payout that one winning contract returns, there may be a gap worth checking.
Same event
Both trades must point to the exact same real-world event. If one market uses different wording or a different deadline, the setup may break.
Opposite outcomes
You are pairing one side with its opposite side on another platform. In a simple Yes/No market, one of those outcomes should win.
Lower than payout
Add the two prices together. If the total is below $1, the leftover difference is the theoretical edge per contract before costs.
Need both fills
The math assumes you can place both orders. If one order fills and the second one moves away, you may no longer have the setup you expected.
Worked Example
Suppose Platform 1 is selling the Yes side at $0.46 and Platform 2 is selling the No side at $0.50 for the same event.
Buy Yes on Platform 1 for $0.46.
Buy No on Platform 2 for $0.50.
Total cost = $0.96. One of those contracts should settle for $1.00.
Potential leftover = $0.04 per $1 payout, or about $4 on a $100 payout size before fees and slippage.
This example only works if both orders fill at those prices, both markets resolve the same way, and costs do not eat the spread.
What To Check Before Clicking Buy
The math is the easy part. Most real-world mistakes happen in execution, rules, or funding.
Liquidity and depth
A quoted price is not enough. Check that there is enough size sitting at that price for your intended order.
Fees and slippage
Even a small spread can disappear after trading fees, gas, bridge costs, or a worse fill than the quote you saw.
Settlement timing
Your capital may be tied up until you can exit or until the market resolves. A slow settlement can change your real return.
Resolution wording
Two markets can look similar but settle differently because of timezone cutoffs, data sources, or special rule clauses.
Funding friction
Moving money between platforms is part of the trade. Delays, limits, and withdrawal policies can make execution harder.
Legal access
Platform availability, KYC, and regional restrictions can stop the trade before you even place the second side.
Risks You Should Understand
This tool is meant to help users think clearly, not to imply that the spread is free money. These are the main ways a simple-looking setup can fail.
No liquidity
If the quoted size is tiny, you may not get your full order filled where the calculator says the edge exists.
Partial fills
One side can fill while the other side does not. That leaves you exposed to a directional position you may not want.
Price movement
The second platform can move while you are placing the first trade, removing the edge before you finish the pair.
Extra costs
Fees, gas, bridging, withdrawals, and spread costs can turn a theoretical edge into a practical loss.
Different rules
Markets with similar titles can still resolve differently because of rule wording, source selection, or event cutoffs.
Access restrictions
KYC requirements, region blocks, and account limits can prevent you from entering or exiting both sides cleanly.
Capital lockup
Even if the math works, your funds may stay tied up until you can close out or wait for settlement.
Platform and custody risk
Execution depends on the platform working, your account staying available, and your funds remaining accessible.
Frequently Asked Questions
Does a green result mean guaranteed profit?
No. A green result only means the simple math shows a gap between combined cost and the $1 payout baseline. Real execution can still fail because of liquidity, fees, slippage, partial fills, or mismatched market rules.
Why must both prices be for opposite outcomes?
This calculator is built for the simplest binary setup. One side should win and the other should lose, so covering both sides only makes sense when they are true opposites of the same event.
Why are prices capped at $1?
The tool assumes each contract settles to $1 if it wins. That is the common framing for binary prediction market shares, so prices should be entered as dollars per $1 payout.
What if the two platforms use different wording?
Then you should treat them as different markets unless you are sure the rules, cutoff times, and resolution source line up. Similar titles are not enough.
Why is liquidity mentioned so often?
Because a quoted price without enough depth is not really tradable at your intended size. Many apparent edges disappear the moment you try to fill both orders.
Will the app eventually show live opportunities?
We are exploring ways to surface live data in the future. For now, this page focuses on manual checks and education.
Disclaimer
This calculator is an educational tool for manually comparing simple two-platform prediction market setups. It does not guarantee profits, does not account for every platform-specific rule or fee, and should not be treated as financial advice. Always verify market wording, liquidity, legal availability, and your own risk tolerance before acting.
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