GambleToolbox / Prediction Markets
Six free manual calculators for Polymarket-style and Kalshi-style binary contracts. Work through entries, fees, exits, arbitrage, liquidity and portfolio risk. No account, wallet or order placement.
Understand contract prices, fees and exit decisions before trading
Use profit and fee tools when the position is still hypothetical. Use sell-versus-hold and slippage when an exit price already exists. Use YES/NO arbitrage only when both contracts describe the same exhaustive event, and portfolio risk only after individual positions are understood.
A 0.40 contract is a market quote. The calculators keep market price, your own probability estimate, fees and executable size as separate inputs so a quoted edge is not confused with a forecast.
The headline price is often only the first available level. A spread can disappear after fees or depth, and a profitable hold estimate can become inferior to selling when liquidity is considered. The tools are designed to be used in sequence rather than as isolated widgets.