Fee Lens for Polymarket

Polymarket's trading fee is not a flat percentage. It follows a curve: fee = shares × rate × price × (1 − price) It peaks at 50¢ and falls away toward either end, which means the headline rate for a category is never what actually lands on your order. Fee Lens puts the real number on screen while you size the trade. WHY IT MATTERS As a share of the money you put at risk, the fee works out to rate × (1 − price). On a 5% market: $100 at 5¢ → $4.75 fee (4.75% of your stake) $100 at 95¢ → $0.25 fee (0.25% of your stake) Same market, same rate, nineteen times the cost. Longshots are taxed hardest, and nothing in the order form tells you that. WHAT YOU SEE • Exact taker fee in dollars, updating as you type • Effective price, once the fee is folded in • Break-even odds — the probability you actually need to be right • Fee as a percentage of your stake • Round-trip cost, and the exit price needed to clear it • The fee curve for that market, with your price marked on it • A running total of fees on trades you have placed RATES ARE READ LIVE, NEVER GUESSED Fee Lens reads each market's own fee schedule from Polymarket's public API. That matters more than it sounds: sports markets currently run two different schedules at the same time, and geopolitics markets carry no fee at all. A built-in rate table would already be showing you wrong numbers. MAKERS PAY NOTHING A limit order that rests on the book is charged no fee, and earns a rebate from the trader who fills it. Fee Lens says so, and shows what the rebate is worth. PRIVACY No account, no sign-up, no analytics, no tracking, no ads, no remote code. The only network requests are to Polymarket's own public API. Your fee history stays in your browser and is never transmitted. The extension is read-only. It cannot place, change or cancel an order. Not affiliated with or endorsed by Polymarket. Fee figures are derived from Polymarket's public API and documentation and may lag changes on their side — always confirm against the order screen before trading. Not financial advice.