Kalshi Arbitrage Calculator, Finder and Polymarket Arbitrage Scanner (2026)

Quick answer: Kalshi Polymarket arbitrage means buying Yes on one platform and No on the other for a combined price under $1.00. Either way, the pair pays exactly $1.00 at settlement. The edge is the gap, minus fees, slippage and the cost of tying up capital. After fees, the gap must usually exceed 3 cents near 50¢ pricing. Most "arbitrage" that scanners flag is not arbitrage at all. It is two contracts with different rules.

What Arbitrage Between Polymarket and Kalshi Means

Arbitrage between Polymarket and Kalshi involves capitalizing on price discrepancies for the same event across both platforms to secure a risk-free profit.

Example: An election market shows Yes at 62¢ on Kalshi and 68¢ on Polymarket.

1. Buy Yes on Kalshi at 62¢.

2. Sell Yes on Polymarket at 68¢. In practice, selling Yes means buying No at 32¢.

3. You have paid 62¢ + 32¢ = 94¢ for a position that pays $1.00 whichever way the election goes.

4. Gross profit is 6¢ per contract, before fees.

Pricing gaps exist because the platforms have different user bases, fee structures and settlement mechanics. They also hold different liquidity on each side. Such gaps are usually small and short-lived, and they often close quickly. Guides on the subject note that professional trading firms capture most cross-platform arbitrage, while retail traders rarely profit after costs. That is why a calculator matters more than the theory.

How Much Do Kalshi and Polymarket Charge? (The Numbers That Decide Everything)

Kalshi fees

Kalshi's general taker fee is round up(M × 0.07 × C × P × (1 − P)), where C is the contract count, P is the price in dollars and M is a per-market multiplier. It applies to orders that match immediately against the book. The fee peaks at 50¢ and shrinks toward both ends of the price range. The fee schedule caps it at $1.75 per 100 contracts at 50¢, with no separate settlement fee.

A separate maker formula, 0.0175 × C × P × (1 − P), applies in markets where the series has a maker multiplier. Kalshi began charging maker fees on resting orders at 11:59 PM ET on August 19, 2026, according to its changelog. Some product families carry their own schedules, so check the specific market.

Polymarket fees

Polymarket runs two venues with different schedules.

• Polymarket US (regulated exchange): The taker fee is 0.06 × C × p × (1 − p), maxing out at $1.50 per 100 contracts at 50¢, with a maker rebate on resting orders. This is from the schedule effective July 1, 2026. One guide lists a flat 0.30% US taker fee, which looks outdated.

• Polymarket international: The fee is shares × feeRate × price × (1 − price), with the rate set by category: geopolitics is free, politics and finance are 0.04, and crypto is 0.07. Makers pay no fee. Sports and several other categories sit at 0.05.

• Deposits, withdrawals and gas: Polymarket charges nothing to deposit or withdraw, and the only network cost is Polygon gas. That cost is typically about a cent per transaction. Conversion and bank-transfer costs on your side are extra.

Two cautions. Older guides still describe Polymarket as fee-free or as charging a 2% fee on winnings. Both look outdated, so confirm against the official schedule. Kalshi's schedule was also revised in July 2026.

Kalshi Arbitrage Calculator: How to Calculate After Fees

A working Kalshi arbitrage calculator needs these inputs:

1. Both entry prices, normalized to a $1.00 payout: Yes on one venue and No on the other.

2. The Kalshi fee: taker or maker, plus the market multiplier.

3. The Polymarket fee: the US or international formula, plus gas.

4. Size in contracts. Kalshi rounds fees up to the next cent, so small lots distort the math.

5. Time to settlement, for annualized return.

Prediction market arbitrage after fees is:

Net profit per contract = $1.00 − (Yes price on Platform A + No price on Platform B) − Fee A − Fee B − gas

Return on capital = Net profit ÷ (total cost + fees)

Worked example (100 contracts, the 62¢/68¢ election market above):

The fee computations are mine, not a source's. Fees consume about half the gross edge. A 3.6% return locked for six months is roughly 7% annualized, before any risk adjustment.

Break-even rule of thumb. If both legs trade near the same price, combined fee drag per contract is approximately:

The gross gap must clear these numbers and still cover slippage. Extreme prices are cheaper to trade because the fee curve flattens. Using maker orders lowers the drag but raises the risk that the other leg moves before you fill.

Kalshi Arbitrage Finder and Polymarket Arbitrage Scanner: What They Do

An arbitrage scanner or finder compares live prices on matched markets and flags gaps. Cross-platform scanners poll both exchanges' order books, normalize contract terms and flag price differences above a threshold you set. Examples, listed without endorsement or testing:

• The Apify Polymarket + Kalshi Arbitrage Finder scans matching binary markets and ranks opportunities by return.

• PredictionMarketsPicks' Arb Scanner compares Kalshi and Polymarket on the same event and scores gaps net of cost rather than on the raw difference.

• PredTerminal combines a cross-platform scanner with whale bet tracking.

• Predicts.guru scans matched markets across Polymarket, Kalshi and Limitless.

• An open-source Python bot on GitHub watches thousands of markets for cross-platform and in-market inefficiencies.

Detection is the easy part. Most arbitrage bots fail their users on execution, not detection. Treat a scanner as a lead generator, then verify everything yourself.

Why "Risk-Free" Arbitrage Isn't

Resolution mismatch is the biggest risk. The two platforms write their own rules, and they differ on settlement source, deadline and the definition of the event. Kalshi binds contracts to a named source agency, while Polymarket's criteria often allow a consensus of credible reporting. Deadlines can differ by roughly 13 hours. The same event can settle in opposite directions on the two platforms. A Cardi B Super Bowl halftime market is cited as a recent example. A paired trade that resolves Yes on both sides, or No on both, costs you one full leg.

Structure can differ too. One guide's example has Polymarket pricing the July FOMC outcome as change buckets while Kalshi uses a rate-threshold ladder, so an apparent locked 3¢ gap became a directional bet with settlement risk.

Different dispute processes. Kalshi resolves markets through its internal team, with an Outcome Review Committee as backstop. Polymarket international uses a bonded dispute process through UMA.

Other risks:

• Execution risk. One leg fills and the other doesn't. Timing risk, regulatory risk and currency risk between pUSD and USD add to it. Traders commonly place the thinner leg first.

• Capital lockup. You need funds on both platforms until settlement, and a 3% edge on a market that resolves in six months may not beat your alternatives.

• Liquidity and slippage. Quoted prices reflect only top-of-book size. Check depth for your full order.

• Access and regulation. Kalshi's sports contracts face state challenges, including a Sixth Circuit loss and Missouri cease-and-desist letters this month. Which Polymarket venue you can use depends on where you live and its terms. Use only venues you are eligible for.

Pre-Trade Checklist

1. Read both resolution rules in full: source, deadline, definition and void rules.

2. Confirm the contracts are genuinely the same event, not look-alikes.

3. Check order-book depth for your size on both sides.

4. Run the net-of-fees calculation with current fee schedules for the exact markets.

5. Factor in gas, funding and conversion costs.

6. Compute return per day of capital locked.

7. Start small, and size so that a total loss on one leg is survivable.

FAQ

Is Kalshi vs Polymarket arbitrage legal?

Trading both platforms is not illegal in itself, but eligibility depends on your location and each platform's terms. Check both before funding either.

Does Polymarket charge fees in 2026?

Yes, on takers, by category and price. Makers pay nothing on the international exchange, and geopolitics markets are free. Polymarket US uses its own formula.

What is the best Kalshi arbitrage calculator?

The best one includes Kalshi's price-based fee formula, Polymarket's category or US fee, gas and rounding at your actual size. Any calculator that uses a flat percentage is unreliable.

Is Kalshi arbitrage betting worth it?

Only when the gap survives fees, slippage and your capital's time value, and when resolution rules match. Many gaps do not.

Why do scanners show gaps that vanish?

Often because they are different contracts, because the book is thin, or because the gap closed before you could fill both legs.