Calculate your exact prediction market payout before you trade. Works for Kalshi, Polymarket, and Robinhood. See why selling early at 98¢ feels disappointing — and what the fees actually cost you.
Platforms
4
Scenarios
Hold + Sell
Updated
Apr 2026
Tool Type
Calculator
See exactly what you'd make — and why — before you click buy. Covers Kalshi, Polymarket, Robinhood, and Coinbase for both holding to resolution and selling early.
Implied probability: 72%
Used in the sell-early comparison below.
The math usually explains the disappointment faster than the platform FAQ does.
This is the most common complaint on Robinhood and Coinbase prediction market forums. The answer is always the same three things:
Spread cost
You paid the ask price to buy. The market is already pricing in some probability of resolution. Buying at 72¢ means the market thinks there's a ~28% chance you lose.
Platform fee
Kalshi charges a formula-based entry fee (up to 1.75¢/contract). Robinhood adds Variable, max $0.01/contract + exchange fee per side. These are small but visible on large positions.
High probability = low upside
Buying a 95¢ contract is risking $95 to make $5. Being right doesn't mean making a lot. The closer to $1 you buy, the less profit is mathematically possible — that's the structure of binary contracts.
These are the pricing assumptions the calculator uses so you can sanity-check the result before you trade.
Fee type: Formula (0.07 × P × (1 − P))
When charged: Entry only
Example at 50¢: 1.75¢/contract (max)
Fee type: Zero (most markets)
When charged: —
Example at 50¢: $0 (politics/econ)
Fee type: Flat Variable, max $0.01/contract + exchange fee
When charged: Both buy & sell
Example at 50¢: Variable, max $0.01/contract + exchange fee × 2 sides
Fee type: Same as Kalshi
When charged: Entry only
Example at 50¢: 1.75¢/contract (max)
Plain-English answers to the payout questions traders hit most often.
Why is my profit so small when I bought at 96¢ and was right?
At 96¢ you paid $96 to earn $100 — that's a maximum possible profit of $4 per contract. Subtract the entry fee (~0.27¢ at 96¢ on Kalshi) and you're left with ~$3.73. High probability = high cost basis = low upside. That's not a fee problem — it's the math of binary contracts.
Why does Kalshi's fee drop to zero near 0¢ or 100¢?
The fee formula (0.07 × P × (1 − P)) produces zero when P approaches 0 or 1. At extreme probabilities the contract is near-certain to resolve one way — the fee structure reflects that. Maximum fee is at P=0.50 (50¢) where uncertainty is highest.
I sold early at 90¢ after buying at 60¢. Why did I make less than I expected?
Spread cost + fees. You paid 60¢ (plus entry fee) and received 90¢ (minus exit fee on Robinhood). The difference isn't just 30¢ per contract — it's reduced by the bid-ask spread and any fees charged on exit. Use the 'Sell Early' tab above to see the exact numbers.
Does Polymarket really charge zero fees?
It depends on which venue. The QCX LLC CFTC-registered exchange (US-only, invite beta) charges a flat 0.75% peak taker fee on Total Contract Premium, with a 0.20% maker rebate — per polymarketexchange.com/fees-hours.html. The global version charges no fees on most markets; crypto carries up to 1.80% at 50¢, select sports up to 0.75% at 50¢. This calculator defaults to zero because the global fee-free structure applies to most traders. If you are trading via the invite-only US venue, apply a 0.75% peak taker fee to your total contract premium.
Are these fee rates guaranteed to be current?
Fee structures are sourced from official platform documentation. Kalshi and Robinhood fee structures have been stable; Polymarket added crypto fees in early 2026. Always confirm the specific market's contract rules before trading — fee schedules can change.
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