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Prediction Market Fee Calculator: Compare Trading Costs
By Odds Reference Published March 4, 2026 Updated July 19, 2026 Editorial Policy
Trading fees determine how much of your profit you keep. Our fee calculator models the cost of any prediction market trade across Polymarket, Kalshi, and Metaculus: enter the contract price, position size, and platform to see the fee in dollars, the net return, and a side-by-side comparison. Small percentage fees can change whether a trade is worth making.
How Do You Use the Fee Calculator?
Enter three inputs into the fee calculator: the contract price (implied probability), the number of contracts or dollar amount, and the platform — Polymarket, Kalshi, or Metaculus. It returns the explicit fee, the net payout if the trade wins, the net return percentage, and a side-by-side platform comparison.
The key output is net return after fees — not the gross payout. A contract bought at $0.80 that resolves to $1.00 looks like a 25% return. After Polymarket’s 2% fee on the $0.20 profit, the net return drops to 24.5%. After Kalshi’s per-contract fee on both entry and exit, the net return might be 23% or lower depending on the fee tier. These differences compound across dozens of trades.
How Do Fee Structures Differ Across Platforms?
Polymarket charges roughly 2% of net winnings only when a contract resolves in your favor; Kalshi charges a flat 1-2 cents per contract on both entry and exit regardless of outcome; Metaculus charges nothing because it runs on reputation points instead of real money.
| Platform | Fee Type | Rate | When Charged | Cost on $100 Position at 50% |
|---|---|---|---|---|
| Polymarket | % of winnings | ~2% | Settlement (winning trades only) | ~$1.00 |
| Kalshi | Per-contract | 1-2 cents | Entry and exit | ~$1.00-$2.00 |
| Metaculus | None | Free | N/A | $0 (reputation-based) |
Rates last verified July 19, 2026 against Odds Reference’s Polymarket and Kalshi platform profiles. Fee schedules move without notice — confirm current terms directly at kalshi.com and polymarket.com before trading. Kalshi publishes its schedule as a CFTC-regulated Designated Contract Market; you can verify that registration on the CFTC’s public site.
Crypto contracts are a partial exception. On March 30, 2026, Polymarket added an explicit taker fee on crypto-category markets specifically, peaking at roughly 1.80% at 50/50 pricing, plus a 20% maker rebate, layered on top of the ~2% settlement fee this calculator models. Politics, sports, economics, and other non-crypto categories are unaffected. See how prediction market fees work for the full rate history, or our Kalshi crypto binary options research for the crypto-specific fee math.
The crossover point matters. For contracts above ~$0.70, Polymarket’s percentage fee applies to a small profit margin, making it cheaper in absolute dollars. For contracts below ~$0.30, the profit margin is large, and 2% of a big win costs more than Kalshi’s flat fee. The calculator models this crossover precisely for your specific trade.
What Does a Fee Comparison Look Like in Practice?
Buying 200 contracts at $0.35 costs $70 up front. If the event happens, Polymarket nets roughly $127.40 after its 2% winnings fee, while Kalshi nets about $126.00 after entry and exit fees — a small gap that widens sharply as the contract price moves away from the middle of the range.
| Metric | Polymarket | Kalshi |
|---|---|---|
| Entry cost | $70.00 | $70.00 + ~$2.00 entry fee |
| Gross payout if win | $200.00 | $200.00 |
| Gross profit | $130.00 | $128.00 |
| Platform fee | $2.60 (2% of $130) | ~$2.00 exit fee |
| Net profit | $127.40 | $126.00 |
| Net return | 182.0% | 175.0% |
At the $0.35 price point, the platforms cost roughly the same. Move the contract price to $0.80 and the comparison shifts. Polymarket’s 2% of a $0.20 profit ($0.80 per 200 contracts) undercuts Kalshi’s flat fee. Move to $0.10 and Kalshi’s flat fee is cheaper than Polymarket’s 2% of $0.90 profit ($3.60 per 200 contracts).
The fee calculator runs these scenarios instantly for any contract price and position size.
How Do Fees Change the EV of a Trade?
Fees subtract directly from expected value: a winning trade’s net profit shrinks by the fee amount, so any EV calculation done before fees overstates the real edge. The effect is proportionally larger on high-probability, low-margin trades, where the fee can erase most of a thin edge entirely.
A contract at $0.85 with a true probability of 90% has a gross EV of:
- EV (before fees) = (0.90 x $0.15) - (0.10 x $0.85) = $0.135 - $0.085 = +$0.05
After Polymarket’s 2% fee on the $0.15 profit:
- Net profit = $0.15 - $0.003 = $0.147
- EV (after fees) = (0.90 x $0.147) - (0.10 x $0.85) = $0.132 - $0.085 = +$0.047
The fee reduced EV by 6%. On thinner edges — a true probability of 87% instead of 90% — fees can flip a marginally +EV trade to -EV entirely. Use the EV calculator alongside the fee calculator to model net expected value before committing capital.
What Hidden Costs Add to Explicit Fees?
Our fee calculator models explicit platform fees. Implicit costs add to the total: bid-ask spreads (1-2 cents on liquid Polymarket markets, 5-10 cents on thin Kalshi markets), currency conversion (0.5-1.5% to buy USDC for Polymarket), and capital lockup on long-duration contracts.
A 5-cent spread on a $0.50 contract is a 10% round-trip cost — far larger than either platform’s explicit fee. Run the numbers on your own position with the fee-adjusted returns calculator, which layers spread assumptions on top of the explicit fee model above.
The Odds Reference dashboard tracks live spreads and prices across platforms, giving you visibility into implicit costs alongside the explicit fees the calculator models.
How Should Fee Structure Influence Platform Choice?
The optimal platform depends on the trade’s profile, not a single headline fee number. High-probability contracts favor Polymarket’s percentage-based fee, low-probability high-payout trades favor Kalshi’s flat per-contract fee, and factors like trade frequency and residency requirements often decide the question before fees even enter the calculation.
- High-probability contracts ($0.70+): Polymarket’s percentage-based fee is small in absolute terms — often the cheaper option
- Low-probability, high-payout trades ($0.05-$0.30): Kalshi’s flat per-contract fee costs less than Polymarket’s 2% of a large profit
- Frequent traders: Kalshi’s predictable flat fee is easier to model across a portfolio; Polymarket charges nothing on losing trades
- Non-US or crypto-native traders: Polymarket avoids banking friction entirely; Kalshi requires US residency and a bank account — see our legal tracker for current state-by-state status
For a head-to-head breakdown of these platforms beyond fees, see the Polymarket vs Kalshi comparison and the broader platform comparison. Sign-up guides for both exchanges are on the platforms hub.
Key Takeaways
- Polymarket charges ~2% of winnings at settlement; Kalshi charges 1-2 cents per contract on entry and exit — each favors different price points (rates last verified July 19, 2026)
- Polymarket layered an additional crypto-only taker fee (peaking near 1.80% at 50/50 pricing) on top of its settlement fee starting March 30, 2026; other categories are unaffected
- The crossover point is around $0.50-$0.70: Polymarket is cheaper above it, Kalshi below
- Fees directly reduce expected value — always calculate EV after fees to assess true profitability
- Hidden costs (spreads, currency conversion, capital lockup) often exceed explicit fees on thin markets
- The fee calculator models exact costs before you trade; the EV calculator confirms whether the trade remains profitable after those costs
Event contracts carry real financial risk regardless of platform or fee structure — fees reduce your edge, they don’t create one. If prediction market trading is affecting your finances or well-being, visit Odds Reference’s responsible gambling resources or call 1-800-522-4700.