Prediction markets · Comparison
Kalshi vs Polymarket for arbitrage
The two biggest prediction markets, side by side: what each charges on sports, who can use them, how you fund them, and how to lock in a profit between the two.
Kalshi
A US exchange regulated by the CFTC. Funded in dollars. Available in the US and many other countries through its website.
Polymarket
An international platform funded with a dollar-pegged digital currency, plus a separate US app on a CFTC-regulated exchange.
The key differences
| Kalshi | Polymarket | |
|---|---|---|
| Sports taker fee | 0.07 × C × P × (1 − P), rounded up to the next cent. MLB series: 0.035 | 0.05 × C × P × (1 − P) |
| At 50¢, per 100 contracts | $1.75 (MLB: $0.88) | $1.25 |
| Maker (resting) orders | 0.0175 in series with maker fees, otherwise free | Free, and sports makers share a 15% rebate pool |
| Currency | US dollars | pUSD, a dollar-pegged stablecoin on Polygon (international platform) |
| Funding | Bank transfer (ACH, free), card (up to 2%), crypto | USDC or other crypto, converted to pUSD |
| United States | Yes | Separate US app, sports markets, rolling out by state |
| Rest of the world | About 140 countries, web only. Not in the UK, Canada, Australia or Ireland, among others | Over 160 countries. Blocked in about 35, including the UK, France, Germany and Australia |
| Limits winners? | No: you trade against other users | No: you trade against other users |
Fees: the same formula, different rates
Both platforms charge the taker a fee based on the price, highest at 50¢ and shrinking toward the extremes:
The difference is the rate. On sports, Polymarket charges 0.05 and Kalshi 0.07, except Kalshi's pro baseball series at 0.035. Kalshi rounds each trade's fee up to the next cent for most accounts. Polymarket rounds to four decimals, and on a buy it takes the fee in shares rather than dollars: at 50¢ and the 0.05 rate you keep 97.5 of every 100 shares you buy.
| Price | Kalshi, standard | Kalshi, MLB | Polymarket, sports |
|---|---|---|---|
| 20¢ | $1.12 | $0.56 | $0.80 |
| 35¢ | $1.60 | $0.80 | $1.14 |
| 50¢ | $1.75 | $0.88 | $1.25 |
| 65¢ | $1.60 | $0.80 | $1.14 |
| 80¢ | $1.12 | $0.56 | $0.80 |
For arbitrage, the fee on both legs is part of the cost. That is why our Kalshi arbitrage calculator applies both platforms' rates automatically.
Who can use which
- In the United States: Kalshi, and Polymarket's US app, which offers sports markets and is rolling out state by state. Polymarket's international platform blocks US users.
- Outside the US: Kalshi's website serves about 140 countries; Polymarket's international platform serves over 160. Neither serves the UK or Australia, and each has its own list of blocked countries, so check both for yours.
Funding and withdrawals
Kalshi works in dollars: a free bank transfer in, a free bank transfer out. Polymarket's international platform runs on pUSD, a dollar-pegged stablecoin on the Polygon network. You deposit USDC or another supported crypto asset, and it is converted for you. Converting money into crypto and back can cost more than the trading fee itself, so plan your funding before your first trade.
How to arbitrage between Kalshi and Polymarket
Many questions trade on both platforms. When YES on one platform and NO on the same question on the other cost less than $1 together, after both fees, every pair pays exactly $1 whatever happens.
Notice how much the fees decide. At 47¢ instead of 45¢, the same trade looks like a 3% gap on prices alone, but after both fees it makes one cent. Always compare prices after fees.
Check that both markets settle the same way. The questions must have the same settlement rules: what counts as a win, what happens in overtime, a postponed game or a draw. If the rules differ, you are holding two separate bets, not an arbitrage.
Which should you use?
- Kalshi if you want to fund in dollars from your bank, or you pair prediction markets with US sportsbooks. MLB series have the lowest fee of all.
- Polymarket if you want the lower sports fee and free maker orders, and you are comfortable funding with crypto.
- Both, if you can. Every extra venue adds price gaps, and arbitrage between the two platforms is only possible if you hold accounts on each.
Run both legs with the real fees.
Open the Kalshi calculatorNew to prediction markets? Start with the complete Kalshi arbitrage guide.
FAQ
Which has lower fees, Kalshi or Polymarket?
For sports, Polymarket. Both use the same formula, but Polymarket's sports rate is 0.05 and Kalshi's standard rate is 0.07: $1.25 versus $1.75 per 100 contracts at 50¢. Kalshi's MLB series, at 0.035, are cheaper than both.
Can you arbitrage between Kalshi and Polymarket?
Yes. Buy YES on one platform and NO on the same question on the other. If the pair costs less than $1 after both fees, every pair pays $1 whatever happens. Both markets must settle by the same rules.
Is Polymarket available in the US?
Polymarket runs a separate US app on a CFTC-regulated exchange it acquired in 2025. It opened to US users in 2026 with sports markets and is rolling out state by state. The international platform blocks US users.
Which is better for sports arbitrage?
Use both. Polymarket has the lower sports fee and free maker orders. Kalshi is funded in dollars and pairs naturally with US sportsbooks. More venues mean more price gaps.
Do Kalshi or Polymarket limit winning traders?
Neither takes the other side of your trades. You trade against other users and the platform earns a fee, so unlike a sportsbook it has no reason to limit you for winning.