Prediction Market Fee Calculator
See how platform fees affect your expected value. Compare Polymarket and Kalshi fee structures to find out what you're really paying.
Fee Calculator
Entry price
Your true probability
Platform
2% fee on net winnings
You'd make $0.045 per share.
How Prediction Market Fees Work
Every prediction market charges fees, but the structures vary. Fees might seem small — 2% here, a few cents there — but they shift your breakeven probability and eat into your edge. A bet that looks +EV before fees might actually be -EV after them.
Polymarket Fees
Polymarket charges a 2% fee on net winnings only. If you lose, you pay nothing extra. Example: you buy “Yes” at 60¢ and it resolves Yes. Your gross profit is 40¢ per share. Polymarket takes 2% of that — 0.8¢ — so your net profit is 39.2¢. The fee only applies to what you actually earned, not your total payout.
Kalshi Fees
Kalshi uses a formula-based fee charged when you place the trade (not at resolution). The taker fee is 7% × price × (1 − price) per contract. This creates a curve where 50/50 markets have the highest fee (~1.75¢ per contract) and extreme-odds markets have almost no fee. Maker orders (limit orders that provide liquidity) pay roughly 4x less.
Why Fees Matter More Than You Think
The real cost of fees isn't the dollar amount — it's how they shift your breakeven probability. Without fees, a 60¢ contract needs a 60% true probability to break even. With Polymarket's 2% fee, the breakeven shifts to about 60.5%. With Kalshi's taker fee, it's roughly 61.5%. That 1-2% shift can turn a marginal +EV bet into a losing one. See the exact breakeven shift for any contract price with our Break-Even Calculator.
Worked Example
You buy 100 shares of “Yes” at 55¢ on Kalshi as a taker. Fee per share: 7% × 0.55 × 0.45 = 1.73¢. Total fee: $1.73. Total cost: $56.73 (vs. $55.00 without fees). If the contract resolves Yes, you receive $100 — profit of $43.27 instead of $45.00. If you made the same trade on Polymarket Global, there's no upfront fee. At resolution, 2% of your $45 winnings is taken: $0.90. Profit: $44.10. On this trade, Polymarket saves you $0.83 per 100 shares. But at different price points, the comparison flips — always run the numbers.
Platform Fee Comparison
| Platform | Fee Structure | When Charged |
|---|---|---|
| Polymarket Global | 2% on net winnings | At resolution (wins only) |
| Polymarket US | 0.10% taker fee | At trade execution |
| Kalshi Taker | 7% × p × (1-p) | At trade execution |
| Kalshi Maker | 1.75% × p × (1-p) | At trade execution |
Common Questions
Which platform has lower fees?
It depends on the contract price. Polymarket's flat 2% on winnings is simpler and usually cheaper for contracts near 50¢. Kalshi's formula-based fee is cheaper for contracts at extreme prices (very high or very low). For most bets in the 30-70¢ range, the difference is small.
Do fees apply if I sell my position before resolution?
On Kalshi, yes — the trading fee applies to every trade. On Polymarket, the 2% winning fee only applies at resolution, but there may be a spread cost when trading in and out of positions.
What's the difference between maker and taker on Kalshi?
A taker is someone who buys at the current asking price (market order). A maker places a limit order that waits to be filled. Makers get lower fees because they provide liquidity to the market. Most casual users are takers.
Should I factor fees into every trade?
Yes. Even small fees compound over time. If you're making 100 trades and each one has 2% less EV than you thought, that's a significant drag on your returns. This calculator helps you see the true EV before you click buy.
What about Robinhood and other new prediction market platforms?
Robinhood, Coinbase, and other platforms entering prediction markets each have their own fee structures. Robinhood has announced commission-free prediction market trading (similar to their stock trading model). As new platforms launch, compare their fees here using the custom fee option — even 'free' platforms may have wider spreads that function like hidden fees.
How do prediction market fees compare to sportsbook vig?
Prediction market fees are generally lower than sportsbook vig. A standard -110/-110 sportsbook line has about 4.5% total margin. Polymarket's 2% on winnings and Kalshi's formula-based fee typically amount to 1-3% total cost. This lower 'tax' is one reason prediction markets are attractive to quantitative traders — less edge is lost to the platform.