High liquidity low fee prediction markets

Why Kalshi wins overall: Current data shows Kalshi with roughly 78% of tracked prediction-market volume over the latest 30-day period, versus about 5% for international Polymarket and 12% for Polymarket US. Kalshi also had about $1.2B in open interest, which is a useful indication of the amount of capital currently committed to positions.defirate.com

That doesn't mean every individual Kalshi market is more liquid—the specific contract matters enormously. For large trades, I'd compare the actual order book and expected slippage rather than simply looking at platform-wide volume.

Fees are more interesting

Kalshi: Its standard fee formula is roughly:

fee = 0.07 × contracts × P × (1-P)

where P is the contract price. Resting orders generally aren't charged the standard trading fee, although certain markets have maker fees.help.kalshi.com

Polymarket: Taker fees vary by category, currently around 4–7% of the probability-weighted component, while makers pay 0% and can receive rebates. Geopolitical/world-event markets are fee-free.help.polymarket.com

So if you're a maker who posts limit orders, Polymarket can be exceptionally attractive. If you're primarily taking liquidity, the difference depends heavily on the contract's price and category.

Robinhood is surprisingly competitive: its commission is now probability-weighted and capped at $0.01 per contract, with Gold users getting a lower rate. However, exchange fees can be added on top.robinhood.com

One important caveat for you in New York

Polymarket's international site currently blocks U.S. trading and directs U.S. users to Polymarket US. polymarket.com Polymarket US is substantially newer/smaller than the international venue, so you shouldn't assume that the enormous global Polymarket liquidity is available to you.

There is also active regulatory litigation around prediction markets in the U.S. A September 2026 federal appeals-court ruling held that Ohio and Tennessee could regulate Kalshi under state gambling laws, creating additional uncertainty around state-by-state access.www.reuters.com

Bottom line

If I were choosing based strictly on your criteria:

🥇 Kalshi — best combination of liquidity + low enough fees + U.S. accessibility

🥈 Polymarket US — potentially better fee economics, but liquidity is currently much smaller

🥉 Robinhood — excellent if you already use Robinhood and value simplicity

One nuance: if you're trading $10k, $50k, or $100k+ positions, I would not choose purely by advertised fees. The effective cost of crossing the spread and moving the order book can dwarf the nominal commission.

If you tell me roughly how much you plan to trade per position (e.g. $500, $5k, $50k) and whether you're trading sports, politics, crypto, or economic events, I can compare the actual effective cost/liquidity of Kalshi vs. Polymarket for that use case.

A breakdown of how they compare on liquidity and fees helps determine the right fit:

• Polymarket
  • Liquidity: The largest decentralized prediction market in the world. It dominates global volume for geopolitics, pop culture, and global world events, featuring massive order books and deep liquidity pools.
  • Fees: Exceptionally low. Geopolitical and world event markets are completely fee-free. For sports markets, it uses a probability-based taker fee peaking at just 0.75% at a 50/50 price point.
  • Access/Requirements: Operates on the Polygon blockchain, meaning you need cryptocurrency (USDC) to fund your account. (Note: Geoblocked for users in the United States unless using compliant workarounds, though regulations shift frequently).
  • Check out the platform details directly on Polymarket.si.com+3
• Kalshi
  • Liquidity: The premier federally regulated (CFTC-regulated) option in the United States. It boasts immense liquidity for U.S.-centric macroeconomics, politics, and increasingly deep pools for major U.S. sports leagues.
  • Fees: Uses a maker-taker model. Taker fees on mid-probability (50\cent ) contracts can peak around 1.75\cent per contract and scale down as probabilities approach 0% or 100%.
  • Access/Requirements: Fully legal and accessible for U.S. residents, allowing standard fiat currency (USD via bank transfer/ACH) without needing a crypto wallet.
  • Explore current contracts on Kalshi.defirate.com+3

To help narrow down the best choice for you, tell me:

• Are you located in the United States or internationally?
• Do you prefer funding your account with traditional currency (USD) or crypto (USDC)?
• What specific topics do you plan to trade the most (politics, sports, macroeconomics, crypto)?