# Prediction Market Handbook

> Plain answers about prediction markets: how odds and fees work, what is legal in the US, how platforms differ, and how accurate the markets are.

Prediction Market Handbook (predictionmarket.fit) is published by Prediction Market Handbook. Articles are AI-assisted, sourced, and reviewed before publication; see https://predictionmarket.fit/editorial-policy/. Market data pages are generated from public Polymarket and Kalshi data and show the time they were last refreshed.

## Data pages

- [How accurate are prediction markets?](https://predictionmarket.fit/accuracy/): Calibration of resolved Polymarket markets: how often contracts priced at each level actually resolved YES.
- [Break-even calculator](https://predictionmarket.fit/tools/break-even/): The probability a contract must win to break even after Kalshi or Polymarket fees.

## Articles

- [Are Prediction Markets Legal in the US? (November 2026)](https://predictionmarket.fit/are-prediction-markets-legal-us.md): As of November 10, 2026, prediction markets are legal under federal law when run as CFTC-regulated exchanges, such as Kalshi and Polymarket US. States argue sports contracts are gambling. Courts have blocked contracts in Michigan, Nevada and Washington, federal appeals courts are split, and three petitions await the Supreme Court.
- [How to Read Prediction Market Odds: Price, Spread and Fees](https://predictionmarket.fit/how-to-read-prediction-market-odds.md): A prediction market price is an implied probability: a YES contract at 62¢ pays $1 if the event happens, so the market prices it at about 62%. Buyers pay the ask, sellers get the bid, and taker fees raise the break-even. On Kalshi, a 62¢ taker buy needs a 63.65% win rate to break even.

## Site

- [About](https://predictionmarket.fit/about/)
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