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Quick Answer

There is no single fee number that makes Polymarket, Kalshi or Opinion cheapest for every trade. Polymarket currently charges takers on fee-enabled markets using category-specific curves and does not charge makers. Kalshi’s fees can vary by contract and some markets may charge makers. Opinion charges takers, does not charge makers under its current policy, publishes a 0%–2% range and applies a $0.50 minimum fee. Compare the live fee preview together with spread and price impact for the exact market and order size.

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Key Takeaways

  • Maker and taker status matters as much as the platform name.
  • Polymarket’s fee coefficient varies by category; some geopolitical markets are fee-free.
  • Kalshi uses market-specific schedules and says some markets may have maker fees.
  • Opinion’s current taker range is 0%–2%, with a $5 minimum order and $0.50 minimum fee.
  • A lower platform fee does not guarantee cheaper execution when spread or price impact is larger.

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Current Fee Structure at a Glance

These structures were verified on August 13, 2026. They are not promises about future pricing.

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Polymarket Fees

Polymarket’s current formula is:
The published coefficient depends on the market category. Current examples include 3% for sports, 4% for politics and finance, 7% for crypto and 0% for geopolitics. Only takers pay. Makers are not charged, and the collected fees support a maker-rebate program. The coefficient is not the same thing as fee as a percentage of trade value. The price × (1 − price) curve peaks at 50 cents and falls toward either end.

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Kalshi Fees

Kalshi says its transaction fee is based on expected earnings on the contract. Its complete fee schedule defines the formula and any market-specific exceptions. Some Kalshi markets may also include maker fees. A resting order is only charged if it eventually executes; canceling an unfilled resting order does not itself create a trading fee. Because schedules can differ for special events or categories, the fee displayed for the exact contract is more useful than a single platform-wide headline number.

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Opinion Fees

Opinion’s published formula applies a topic-level rate, the market price and any available discounts:
The current published range is 0%–2%. Makers are not charged; takers pay when an order executes immediately. Opinion lists a $5 minimum order and a $0.50 minimum fee. Discounts can reduce the curve-based amount, but the floor still applies. Read Opinion Fees Explained for worked examples and the maker/taker edge cases.

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A Fair Way to Compare Fees

Use the same order scenario on each venue:
  1. Choose the same event and equivalent outcome rule.
  2. Use the same intended order size.
  3. Check whether the order would make or take liquidity.
  4. Record the displayed fee.
  5. Estimate the average fill using available depth.
  6. Add any funding or withdrawal-provider costs separately.
The comparison should be:
For a position you plan to close before resolution, repeat the calculation for the exit. A round trip can involve two fees and two spreads.

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Why Small Trades Need Extra Attention

Minimum fees and rounding rules matter most at small sizes. On Opinion, a $0.50 floor on a $5 order represents a much larger percentage than the same floor on a $500 order. On Kalshi, rounding and market-specific terms can change the result. Polymarket’s very small calculated fees can round according to its published precision rules. Do not compare only the formula. Enter the actual order size in each live interface.

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Where Opinion Fits

Opinion’s current structure is straightforward: makers are fee-free, takers follow a market- and price-sensitive curve, and a minimum fee applies. That can favor resting limit orders, but waiting introduces non-fill risk. Users who need immediate execution should compare the fee with the live spread and depth.

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What to Watch

  • Category or contract-specific fee changes.
  • Maker-rebate and liquidity programs.
  • Minimum fees or rounding rules on small orders.
  • Whether a limit order actually rests or crosses the book.
  • Funding-provider, bridge or withdrawal costs outside trading.

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FAQ

It depends on the exact market, order type, price and size. Compare the live fee plus spread and price impact rather than choosing from one headline rate.
Polymarket’s current trading-fee documentation says makers are not charged. Only takers pay on fee-enabled markets.
Some Kalshi markets may have maker fees. Check the current fee schedule and the information icon beside the order before trading.
Opinion’s current policy does not charge makers. A limit order can still become a taker if it executes immediately against an existing order.
The official Docs currently list a $0.50 minimum fee and a $5 minimum order. These values can change.
Polymarket and Opinion use probability curves containing price × (1 − price). The value is highest at 0.50, where the outcome is most uncertain.Educational information only. Prediction-market trading involves risk, and access or eligibility varies by jurisdiction.

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Sources & References

  1. Polymarket Docs — Fees — Current category coefficients, taker-only fee structure and maker rebates
  2. Kalshi Help Center — Fees — Current transaction-fee and maker-fee guidance
  3. Kalshi — Fee Schedule — Current market-specific formulas and schedules
  4. OPINION Docs — Fees — Current fee range, maker/taker policy, formula, discounts and minimums
All sources verified 2026-08-13. Prediction-market terms change frequently — verify against each platform’s current documentation before treating these numbers as decision-quality data. Editorial content, not investment or gambling advice.