Break-even calculator

Fee formulas as published by Kalshi (schedule effective July 7, 2026) and Polymarket (fee docs as of November 10, 2026)

Short answer

Break-even probability = (price + fee per contract) / $1. A 62¢ Kalshi taker buy of 100 contracts pays a $1.6492 fee, so it must win 63.65% of the time to break even.

To break even, this contract must win

63.65%

Fee $1.6492. Total cost $63.6492. If YES wins you receive $100.00, a profit of $36.35.

The formulas

Kalshi: fee = 0.07 × C × P × (1 − P) for takers, rounded up to the nearest $0.0001. Maker fees in most markets are 0.
Polymarket: fee = C × rate × P × (1 − P), charged to takers. The rate depends on the market category.

C is the number of contracts and P the price in dollars. The full derivation, with worked examples, is in How to read prediction market odds. Fees change, so check the venue's current schedule before trading. This is not financial advice.