Calculator
Run the fee calculator before you decide whether a trade is actually worth your attention. It is especially valuable in thin markets, fast markets, or any setup where the expected edge is only a few percentage points.
Trade setup
Choose the setup, then enter price and size.
Fee assumptions
Enter the fees that apply to your exact venue, order type, and cash transfer path.
Table of Contents
What counts as trading cost in prediction markets
Traders frequently undercount costs because they think only about explicit trading fees. In practice, the money lost to friction can come from multiple layers: platform fee schedules, settlement charges, bank or chain transfer costs, and the operational cost of moving money between venues.
For strategy work, it is better to slightly overestimate friction than to model a trade too optimistically. A professional process protects itself from unpleasant surprises at the execution layer.
- Entry fees on the initial buy
- Exit fees when closing the position or collecting settlement proceeds
- Deposit, withdrawal, bridge, or network costs
- Any other flat expense required to complete the workflow
How to use the fee calculator correctly
Start by choosing the scenario that matches the real trade. If you expect to exit before resolution, use the round-trip mode because it models the cost stack on the way in and on the way out. If you plan to hold to settlement, use the settlement modes so the outcome reflects that path instead.
Then enter the actual trade size in contracts, not the maximum capital you might deploy someday. The calculator is most useful when it reflects the order you are about to place, because that is when breakeven price and total fee load become operationally relevant.
- 1Choose round-trip or settlement mode based on your actual intended exit path.
- 2Enter price and contracts for the specific order size you expect to execute.
- 3Add entry and exit fee rates from the venue or product you are trading.
- 4Include fixed cash costs such as withdrawals, gas, or bank movement.
Worked fee example
Assume you buy 500 contracts at $0.47, expect to exit at $0.58, pay 0.10% on entry and exit, and spend $5 to withdraw. On the surface, the move from $0.47 to $0.58 looks clean, but the fee calculator reveals how much of that gain survives once the full workflow is priced correctly.
This matters most for traders who scalp or rebalance often. Even small fee rates become material when multiplied across frequent entries and exits, especially if the strategy depends on capturing only modest directional moves.
- Higher turnover strategies need stricter fee discipline than hold-to-resolution trades.
- Flat fees matter more on smaller position sizes because they are spread over fewer contracts.
- The breakeven exit price tells you whether the planned trade has enough room to matter.
Common mistakes when modeling prediction market fees
One common mistake is using a preset and never checking whether the exact product or order type matches the preset assumptions. Another is treating transfers as irrelevant because they are not charged by the market itself, even though they still reduce realized profit.
The third mistake is believing the gross PnL is the strategy. In reality, the tradable strategy is net PnL after all repeatable costs. That is the number you can compound.
- Ignoring fixed costs because they look small in isolation
- Using theoretical position size instead of executable order size
- Forgetting that both the open and close leg can have friction
- Comparing venues without normalizing their full cost path
If the trade only works under unrealistically low fees, it does not really work. Build your go or no-go rule on the conservative version of the cost stack.
Sources
These references support the assumptions and workflow guidance on this page. Always verify current platform rules before relying on a calculator preset.
Official Polymarket documentation describing fee handling and product-specific fee notes.
Kalshi help documentation describing fee schedules and cost considerations by contract type.
Frequently Asked Questions
Short, practical answers to the questions readers usually ask after learning how prediction markets price, trade, and settle.