What this page sets up
The calculator opens on the Kalshi and Polymarket tab: 100 Kalshi contracts at 40¢ with the standard taker fee. Pick the platform, type the price in cents and the number of contracts, and choose the fee: Kalshi’s coefficient (editable, for markets with their own fees) or the Polymarket market’s category. The result shows what the contracts pay if the outcome happens, the odds before and after the fee, and the win rate you need to break even.
Reading the result
The price is the market’s implied probability, and 1 ÷ price is the decimal odds you’d get without a fee. The fee is charged on top of the price, so the odds after it are a little shorter: 100 contracts at 40¢ cost $41.68 with Kalshi’s fee and pay $100, decimal odds of 2.399 instead of 2.50. The fee is largest in cents at 50¢ and smallest near 1¢ and 99¢, so it takes the biggest share of the price on cheap contracts. A direct Kalshi member’s fee is rounded to $0.0001; through a broker (FCM) it is rounded to the cent, which can take a large share of a cheap single contract: pick the account type under the fee.
What the fee doesn’t cover
The calculator assumes you hold the contracts until the market settles. Selling early is another trade with its own fee. Kalshi charges up to 2% on card deposits and lets some markets trade fractions of a contract (the calculator uses whole contracts). Polymarket charges fees only on markets that have them, pays some takers rebates, and charges nothing to deposit or withdraw, though intermediaries such as card or crypto on-ramps may.
Comparing with a sportsbook
Type the sportsbook’s American odds for the same outcome into the comparison box. The calculator stakes the same total at the sportsbook and tells you which pays more. This is maths only: we don’t link to any platform or sportsbook, and prediction markets and sports betting are legal in some places and not others.
Fees and odds on 100 contracts
Kalshi's standard taker fee (0.07, rounded for a direct member) and Polymarket's sports rate (0.05) on 100 contracts at common prices, and the decimal odds once the fee is paid.
| Price | Implied | Odds, no fee | Kalshi fee | Kalshi odds after | Polymarket fee | Polymarket odds after |
|---|---|---|---|---|---|---|
| 1¢ | 1% | +9900 · 100.00 | $0.0693 | 93.519 | $0.0495 | 95.283 |
| 5¢ | 5% | +1900 · 20.00 | $0.3325 | 18.753 | $0.2375 | 19.093 |
| 10¢ | 10% | +900 · 10.00 | $0.63 | 9.407 | $0.45 | 9.569 |
| 20¢ | 20% | +400 · 5.00 | $1.12 | 4.735 | $0.80 | 4.808 |
| 30¢ | 30% | +233.33 · 3.333 | $1.47 | 3.178 | $1.05 | 3.221 |
| 40¢ | 40% | +150 · 2.50 | $1.68 | 2.399 | $1.20 | 2.427 |
| 50¢ | 50% | +100 · 2.00 | $1.75 | 1.932 | $1.25 | 1.951 |
| 60¢ | 60% | −150 · 1.667 | $1.68 | 1.621 | $1.20 | 1.634 |
| 70¢ | 70% | −233.33 · 1.429 | $1.47 | 1.399 | $1.05 | 1.407 |
| 80¢ | 80% | −400 · 1.25 | $1.12 | 1.233 | $0.80 | 1.238 |
| 90¢ | 90% | −900 · 1.111 | $0.63 | 1.103 | $0.45 | 1.106 |
| 95¢ | 95% | −1900 · 1.053 | $0.3325 | 1.049 | $0.2375 | 1.05 |
| 99¢ | 99% | −9900 · 1.01 | $0.0693 | 1.0094 | $0.0495 | 1.0096 |
Sources: Kalshi's current fee schedule is dated July 7, 2026; its rates match the February 5, 2026 copy (archived) we cite for the coefficients, and Fee Rounding, read September 26, 2026, for rounding; Polymarket, Trading fees, read September 26, 2026. Maths only, not trading advice.
Maths only, not betting advice. If gambling stops being fun, free confidential help is listed on the odds calculator page.