Vig, spread, and market structure differences between Kalshi and Polymarket explained.
Price Gap
2-5¢ typical
Kalshi Fee
Built in
Poly Fee
0% maker
Read Time
9 min
It's not manipulation. It's fee structure, liquidity, and market category. We'll show you when the gap matters and when it doesn't.
Kalshi can price the same event higher once fee structure is included
Polymarket often looks tighter on liquid fee-bearing markets
Directional comparison based on documented fee structures and live order-book mechanics.
Kalshi charges 0.07 × P × (1 − P), max 1.75¢/contract at 50¢ markets — applied to both YES and NO buyers. Polymarket uses probability-based rates (0.75% at 50¢ sports, 1.80% at 50¢ crypto).
Overround reflects bid/ask spread. Thinner markets widen spreads. Kalshi has deeper liquidity on US economic and policy events; Polymarket runs deeper on global events and crypto.
Politics and policy markets: zero taker fees, zero maker fees Polymarket now charges up to 1.00% on politics markets (as of March 30, 2026). For a political market, Kalshi may actually be cheaper despite a higher nominal ask price.
The same event may have different resolution criteria on each platform. A price gap that looks like overround may reflect genuine probability disagreement — not just cost. This is NOT the same as exploitable arbitrage.
Illustrative examples — actual prices change in real time. These show fee structure, not live data.
| Scenario | Platform | Ask Pricing Driver | Fee Note |
|---|---|---|---|
| Fed rate cut (50¢ market) | Kalshi | Taker fee up to 1.75¢/contract | Fee formula peaks at 50¢ |
| Fed rate cut (50¢ market) | Polymarket | Economics: ~1.50% peak | Lower peak for this category |
| Political outcome (50¢ market) | Kalshi | Zero taker fee | Politics = zero fees (cheapest) |
| Political outcome (50¢ market) | Polymarket | Up to 1.00% peak | New category fee since Mar 30, 2026 |
| Crypto direction (50¢) | Kalshi | N/A — not listed | Category restriction |
| Crypto direction (50¢) | Polymarket | Up to 1.80% peak | Highest PM category fee |
The honest answer: rarely. First, the gap looks larger than it is — Kalshi charges zero fees on politics markets (the most-compared category), so a visible price difference there usually vanishes after accounting for fees. Second, when a real gap does exist after fees, resolution rule differences create serious risk: a contract Kalshi resolves YES may resolve NO on Polymarket if the underlying criteria differ. That risk can exceed the visible spread.
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