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Most markets on Polymarket US support fractional contracts, so you can buy or sell part of a contract. These markets trade in steps of 0.01 contracts (1% of a contract). A small number of markets, mostly futures, still trade in whole contracts only.

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How It Works

When you buy using a dollar amount, the system purchases as many contracts as that amount can cover at the current market price, rounded down to the market’s step size: 0.01 contracts on most markets, or 1 contract on whole-contract markets. The amount you enter also covers the trading fee. Any amount left over stays in your cash balance.

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Example

You want to spend 100 dollars to buy Yes contracts priced at $0.65. To keep the math simple, this example leaves out the trading fee:
  • Each contract costs $0.65
  • 100 ÷ 0.65 = 153.846… contracts
  • On a market that trades in 0.01-contract steps, that rounds down to 153.84 contracts
  • On a whole-contract market, it rounds down to 153 contracts
In practice, part of your $100 pays the trading fee, so you receive slightly fewer contracts. See the Fee Schedule for how the fee is calculated.

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Key Points

  • Most markets support fractional contracts in steps of 0.01 contracts; a small number still trade in whole contracts only
  • When buying with a dollar amount, you receive the most contracts that amount can cover at the current price, after the trading fee, in the market’s step size
  • Any amount left over stays in your cash balance