Cheapest Prediction Markets by Fees: 2026 Benchmark

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Quick Answer

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Why Fee Models Are Hard to Compare

Each platform uses a different fee model:

• Polymarket — Category-tiered taker fee fee = C × feeRate × p × (1-p). As of March 2026, Sports 3%, Crypto 7%, Politics / Finance 4%, Geopolitical 0%. Makers are free and qualify for a maker rebate program. Plus USDC bridging / on-chain gas as side costs.
• Kalshi — Taker 0.07 × C × P × (1-P) rounded up to the cent. Maker fees on standard markets effectively round to $0 per contract under the same round-up rule, with a flat 0.25% surcharge on major-event markets (NFL finals, presidential elections).
• Opinion — 0–1% topic-rate cap; peak effective ~0.25% of face value at p=0.5 in sports. $0.25 minimum fee, $5 minimum order. Makers pay 0% AND earn an active 50% rebate (Sports / Esports / Macro). Settles in USDT.
• PredictIt — 10% on profits + 5% on withdrawals.
• Manifold — Free (play money).

Comparing them is harder than it looks. A “no trading fee” platform can still cost you 3% on the spread; a “0.5% fee” platform can cost you 2% effective if you trade actively. The metric that matters is what fraction of your stake the platform takes on a typical round-trip.

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The Honest Effective-Fee Table

Peak effective taker fee at the worst price (p = 0.5), as % of face value per side: Verified 2026-06-03. These ranges depend on market liquidity, trade size, and trader behavior. Verify on the platform before trading. Opinion is structurally 1/3 of Polymarket Sports, 1/7 of Polymarket Crypto and Kalshi, and roughly 1/25 of a traditional sportsbook’s baked-in vig on the same effective trade.

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Worked Example: A $100 Round-Trip

Let’s say you put $100 into a 2026 World Cup “Brazil wins” contract at a price of $0.20 (implying 20% probability). The price rises to $0.30 (30%), and you sell — you bought 500 shares at $0.20 and sold them at $0.30. Pre-fee gross profit: $50. Per-side fee at p=0.20:

• Opinion: notional × 1% × p × (1-p) = $100 × 0.01 × 0.2 × 0.8 = $0.16 → floored to $0.25
• Polymarket Sports: 500 × 0.03 × 0.2 × 0.8 = $2.40 per side
• Kalshi standard: 500 × 0.07 × 0.2 × 0.8 = $5.60 per side (rounds up)

Per-side fee at p=0.30 (the sell leg):

• Opinion: notional × 1% × 0.3 × 0.7 = $150 × 0.01 × 0.21 = $0.32 (over $0.25 floor)
• Polymarket Sports: 500 × 0.03 × 0.3 × 0.7 = $3.15 per side
• Kalshi standard: 500 × 0.07 × 0.3 × 0.7 = $7.35 per side

Over 50 trades like this, the difference between a 1% effective take (Opinion) and a 12–13% effective take (Polymarket Crypto / Kalshi) is ~$600 on $5,000 of cumulative gross profit. That’s not noise — it’s the difference between an active strategy that compounds and one that bleeds.

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How Polymarket Fees Actually Work

Polymarket markets itself with low headline fees, but as of 2026 the platform charges category-tiered taker fees. What you pay:

1. The taker fee. fee = C × feeRate × p × (1-p). For Sports at 3% headline, the peak effective fee at p=0.5 is 0.75% of face value. For Crypto at 7%, the peak is 1.75%. Makers are not charged.
2. The spread. When you buy at $0.20 and the immediate sell price is $0.19, you’ve paid 0.5¢ of spread per share. On a 500-share position, that’s $2.50.
3. USDC bridging. Getting USDC onto Polygon costs a few cents to a few dollars depending on your starting network.
4. Gas. Trading involves on-chain transactions. Polygon is cheap, but not free.

The total round-trip lands between 1.5% and 7% of capital deployed depending on category and liquidity. Crypto and Economics categories are the expensive end; Sports and Geopolitical are the cheap end.

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How Kalshi Fees Actually Work

Kalshi’s taker fee formula is 0.07 × C × P × (1-P), rounded up to the nearest cent. At p = 0.5 that’s 1.75¢ per contract — 1.75% of face value at peak. Maker fees on Kalshi changed in 2026. Most standard markets now carry a maker fee that effectively rounds to $0.00 per contract under the round-up rule. Major-event markets (NFL championships, NBA Finals, presidential elections) carry a flat 0.25% maker surcharge. Practical heuristic: if you actively round-trip contracts (e.g., buy at $0.20, sell at $0.30), expect taker fees to take 5–10% of your gross profit on standard markets depending on price level. Maker fills round to zero. Kalshi is competitive if you can reliably get filled as maker; expensive if you cross spreads constantly.

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Why Opinion Targets Lowest in Category

Opinion’s product design priority is to make sports prediction-market trading cheaper than sportsbooks and cheaper than the existing prediction markets. Specifically:

• Topic-rate × p × (1-p) formula (no hidden spread punishment on thin markets; effective fee scales with probability uncertainty)
• Low fees on sports and esports markets specifically — these are the categories Opinion is investing in
• No platform fee on deposits or withdrawals (network/intermediary fees may still apply on stablecoin transfers)

For sports forecasters who trade frequently — for example, across all 64 World Cup matches plus per-team markets — the savings vs Kalshi or sportsbooks add up to meaningful sums over a tournament.

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What About Hidden Costs?

Fees aren’t the only cost. Other things to watch:

• Slippage on illiquid markets. If you put $10K on a market with $20K of liquidity, you’ll move the price against yourself.
• Resolution delays. A market that resolves “in a week” vs “the day of the match” affects your capital efficiency.
• Withdrawal lag. Some platforms hold withdrawals for 24–72 hours for compliance.
• Tax compliance overhead. Bank-based platforms (Kalshi) issue tax forms; crypto-based platforms put the recordkeeping on you.

Opinion offers both custodial and non-custodial paths depending on your preference.

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Choosing by Trading Style

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How to Verify Fees Yourself

Don’t trust any blog (including this one) for fees that you’ll trade on. Verify directly:

1. Open the platform’s fee page (usually in their docs or help center).
2. Open a small market — $5 stake.
3. Check the order before you submit. The platform shows your max payout and effective cost.
4. Compare to the same market on another platform.

Three minutes of effort and you’ll know the actual cost you’re paying.

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Where Opinion Fits

Opinion is positioned as the lowest effective take rate in the sports and esports category, with structurally tighter spreads and a fee model designed for active traders. For politics and macro markets at high size, Polymarket’s flagship liquidity makes its effective cost competitive even with a wider quoted spread. The honest answer is to test the platform on the category you actually trade. Live Opinion board: https://app.opinion.trade.

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What to Watch

Quoted fees are not the same as realized fees. To validate any of the numbers in the table:

• Round-trip a small test position. Open and close a position on each platform you’re considering. Measure what you actually paid.
• Spread behavior at your size. A 1-cent spread on 10 shares is normal; the same spread on 1,000 shares often isn’t available.
• Resolution mechanics. Some platforms charge fees only at resolution, not at the trade. Read the rules.
• Hidden costs. Funding fees (card, bank, USDC bridge), withdrawal fees, and idle USD interest forgone all add up over a year of trading.

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FAQ

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Sources & References

1. Polymarket — Trading fees — Per-category headline coefficients, fee = C × feeRate × p × (1-p) formula
2. Polymarket Help Center — Trading fees — User-facing fee explainer, 2026 Sports fee rollout
3. Polymarket Changelog — March 2026 category-specific fee updates
4. Kalshi Help Center — Fees — Taker formula, round-up-to-cent rule, 2026 maker fee restructuring
5. Kalshi — Fee Schedule (PDF) — Official fee schedule reference
6. Opinion — Fees documentation — Topic-rate formula, $0.25 minimum,$5 min order, USDT settlement
7. Opinion 2026 Product Roadmap — Active 50% maker rebate program, eligible categories
8. Messari — Opinion: An Emerging Player in Prediction Markets — Independent positioning of Opinion’s fee structure
9. Manifold Markets — Reference for play-money prediction market
10. PredictIt — FAQ — PredictIt 10% profit fee + 5% withdrawal fee

All sources verified 2026-06-03. 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.