Kelix / Learn
Prediction markets, worked out.
Short guides with the formulas, tables and worked examples behind Kalshi, Polymarket and sports prices. Written for people who would rather test an idea than trust it.
Basics · 7 min
How prediction markets work
What prediction markets are, how a $1 event contract is priced, what a 63-cent price means, how settlement works and where the price stops being a probability.
Costs · 6 min
Prediction market fees, worked out
Kalshi and Polymarket both charge fees shaped like p × (1 − p). See the formula, fee tables at every price, rounding effects, and how fees move your break-even probability.
Strategy · 7 min
Kalshi–Polymarket arbitrage, honestly
How cross-platform prediction market arbitrage works, a worked example where a 3-cent gap becomes 1 cent of profit after fees, and the settlement risks that break “risk-free” trades.
Automation · 9 min
Building an AI trading bot for prediction markets
The five parts of a Kalshi or Polymarket trading bot, Kelly sizing for $1 contracts, how LLM look-ahead leakage ruins backtests, and a test plan before real money.
Strategy · 8 min
Seven prediction market strategies, and how each one fails
Model-versus-market, arbitrage, market making, news speed, rules reading, longshot fading and near-certain contracts. What each prediction market strategy needs and how it breaks.
Sports · 7 min
Sports prediction markets vs. sportsbooks
How sports event contracts on Kalshi, Polymarket and Robinhood differ from sportsbook odds: who sets the price, how to remove the vig, and how to compare a moneyline with a contract price.
Policy · 6 min
Are prediction markets legal? The 2026 fight, explained
Why the CFTC and states disagree over prediction markets, what the 3rd, 6th and 9th Circuit rulings said in 2026, Minnesota’s ban, and what it means for traders. Updated November 2026.
Research · 6 min
Are prediction markets accurate?
How to measure prediction market accuracy with calibration and Brier scores, why a 70% favorite losing is not a miss, known biases like the longshot effect, and how to compare a model with a market.
Tools
Convert prices with the odds calculator, compare models and markets in Kelix Lines, read Kalshi vs Polymarket, or learn how prediction market backtesting works.