Home › Tools › Polymarket arbitrage calculator

Polymarket Arbitrage Calculator

Free · runs in your browser · live examples updated November 7, 2026

An arbitrage holds both sides of the same event on two exchanges so that one of them always pays $1. It works only when the two prices plus fees cost less than $1. Right now (November 7, 2026) the cheapest pair we track is Will Anthropic or OpenAI IPO first: OpenAI on Polymarket at 2.2¢ plus Anthropic on Kalshi at 93.5¢ costs 96.2¢ with fees at midpoint prices.

Arbitrage calculator

Price of side A (cents) — e.g. YES on Polymarket Fee on side A Price of side B (cents) — the other outcome, on the other exchange Fee on side B Number of shares / contracts on each side Days until both markets resolve

Total cost incl. fees—

Guaranteed payout—

Profit (or loss)—

Return—

Annualized—

Polymarket taker fee = shares × rate × p × (1 − p); Kalshi general taker fee = 0.07 × contracts × P × (1 − P), rounded up to the next cent. The payout is guaranteed only if both markets resolve on identical rules.

Live cross-exchange pairs

Two-outcome events listed on both Polymarket and Kalshi, with the cheaper way to hold both sides at midpoint prices (real asks are higher). A cost under 100¢ is a gross margin; over 100¢ is a loss.

Event	Polymarket	Kalshi	Fees	Cost	Result per $1	Ends
Will Anthropic or OpenAI IPO first	OpenAI 2.2¢	Anthropic 93.5¢	0.51¢	96.2¢	+3.8¢	2028-01-01
US recession by the end of 2026	No 95.5¢	Yes 2.5¢	0.39¢	98.4¢	+1.6¢	2026-12-31
Which party wins the 2028 presidential election	Republicans 32.5¢	Democrats 65.5¢	2.46¢	100.5¢	-0.5¢	2028-11-08

Why most arbitrage is not free money

⚠️ Access. Kalshi serves US residents; polymarket.com is close-only for US users (Polymarket in the United States). Few traders can legally use both.
⚠️ Rules. The two markets must resolve on the same facts, sources and deadline. Wording differences can make both sides lose.
⚠️ Prices. Midpoints are not fills: you buy at the ask, and large orders move the price.
⚠️ Time. Money is locked until both markets settle — a 3% margin over two years is about 1.5% a year.

See the full side-by-side on Polymarket vs Kalshi odds today.

Try it on live markets

Put real prices into the calculator: every page below shows current odds, 24-hour moves and the market rules.

Fed rates odds · 2028 election odds · NBA odds

Most traded right now:

US-Iran effective ceasefire continues? Through November 5 99%
Republican Presidential Nominee 2028 J.D. Vance 37%
Democratic Presidential Nominee 2028 Jon Ossoff 27%
Israel x Iran ceasefire continues? Through November 4 100%
Presidential Election Winner 2028 JD Vance 19%

Frequently asked questions

Can you arbitrage Polymarket and Kalshi?

Only when the two prices plus fees add up to less than $1 for the same outcome set, the rules match, and you can legally use both platforms — which is rare, because Kalshi serves US residents and polymarket.com is close-only in the US.

How are fees included in the calculation?

Polymarket charges takers shares × rate × p × (1 − p) with a category rate; Kalshi's general taker fee is 0.07 × contracts × P × (1 − P), rounded up to the next cent. The calculator adds both to the cost.

What is a good arbitrage margin?

Anything above zero after fees is a gross profit, but compare it with the time until settlement: annualize it, and weigh the rule and access risks before trading.

🔔 Free Telegram watchlist of big odds moves

All tools · Polymarket fees · Polymarket vs Kalshi odds · Polymarket odds today. Polymarket View is independent and not affiliated with Polymarket, Kalshi or any sportsbook. Educational math, not financial or betting advice.

Reading metrics and privacy