Prediction market payout calculator
Enter a contract price and your stake. Get payout, net profit after fees, ROI and the win rate you actually need to break even — with the real fee formula for Kalshi, Polymarket (by market category) and Polymarket US applied.
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Prediction market contracts settle at $1 or $0 — there is no partial outcome. A losing position loses everything you paid for it.
Fee schedules as of 10 Jul 2026 (Polymarket), 1 Jul 2026 (Polymarket US) and Sep 2026 (Kalshi, checked 14 Sep 2026). Sources: Polymarket fees, Polymarket US fee schedule, Kalshi fee schedule. Venues revise fees; verify before trading.
How the math works
A contract is a claim on $1. Its price is the market's probability estimate: 28¢ means "the market thinks this happens 28% of the time." Buy 100 contracts at 28¢ and you pay $28; if the event happens you receive $100.
That asymmetry is why price and probability are the same conversation. Your edge is not "will this happen" — it's "does it happen more often than the price implies, after fees."
Kalshi's fee formula
Kalshi charges 0.07 × contracts × price × (1 − price), rounded up to the next
cent, on taker orders. Because the formula multiplies price by its complement, the fee is
largest on coin-flip markets and smallest at the extremes:
| Price | Taker fee per contract | Maker fee per contract |
|---|---|---|
| 5¢ | 0.34¢ | 0.09¢ |
| 25¢ | 1.32¢ | 0.33¢ |
| 50¢ | 1.75¢ (maximum) | 0.44¢ |
| 75¢ | 1.32¢ | 0.33¢ |
| 95¢ | 0.34¢ | 0.09¢ |
Maker orders — resting limit orders that add liquidity — are charged per series. Where a maker fee applies, the published multiplier is 0.0175, i.e. 25% of the taker fee; many series charge makers nothing. On balanced markets that difference is roughly 1.3¢ per contract, which is often larger than the edge itself.
Polymarket's fee formula
Since March 2026 Polymarket charges takers rate × contracts × price × (1 − price),
where the rate depends on the market's category. Makers are never charged. The shape is the
same as Kalshi's — peak at 50¢, near zero at the extremes — but the coefficient is lower on
most categories and zero on geopolitics:
| Category | Taker rate | Max fee per 100 contracts (at 50¢) |
|---|---|---|
| Crypto | 0.07 | $1.75 |
| Sports, economics, culture, weather, other | 0.05 | $1.25 |
| Politics, finance, tech, mentions | 0.04 | $1.00 |
| Geopolitics | 0 | $0.00 |
Worked example: 100 contracts on a politics market at 45¢ cost
0.04 × 100 × 0.45 × 0.55 = $0.99 in fees. The same trade in crypto costs $1.73.
Polymarket US — the separate CFTC-regulated exchange — uses a flat 0.06 taker coefficient
(max $1.50 per 100 contracts) and pays makers a 0.0125 rebate, rounded to the cent.
Why break-even probability matters more than payout
A 3.5× payout looks impressive until you notice it corresponds to a 28% break-even rate. The question is never "how much could I win" — it's whether your estimate of the probability beats the price by more than the fee. That gap is what FluxrBot measures a thousand times a day across live news feeds.
Common questions
How is profit calculated on a prediction market?
Each contract settles at $1 if the event happens and $0 if it doesn't. If you buy at 28¢, every contract returns 72¢ profit on a win and loses the 28¢ you paid on a loss. Profit = contracts × (1.00 − price) minus fees.
How much does Kalshi charge in fees?
Kalshi's taker fee is 0.07 × contracts × price × (1 − price), rounded up to the next cent on the order. The fee peaks at 50¢ (1.75¢ per contract) and shrinks toward both extremes. Maker fees vary by series; where charged, the published multiplier is 0.0175 — 25% of the taker rate — which is what this calculator uses.
Does Polymarket charge trading fees?
Yes. Polymarket charges a taker fee on most categories since March 2026: fee = rate × contracts × price × (1 − price), with rates from 0.04 (politics, finance, tech) to 0.07 (crypto). Geopolitics markets are fee-free, and makers are never charged. Polymarket US, the CFTC-regulated exchange, charges a flat 0.06 taker fee and pays makers a 0.0125 rebate. Pick the venue and category above to model the exact number.
What is break-even probability?
It is the win rate you need for the trade to be neutral over many repetitions. At a price of 28¢ with fees included, you need to win slightly more than 28% of the time to break even.