Market Edge Calculator

Market edge is the gap between the market's implied probability for an event and your own probability estimate. If a Kalshi contract trades at 62¢, the market is saying the event has roughly a 62% chance of happening. If your independent analysis suggests the true probability is closer to 70%, you have an estimated +8 percentage-point edge on the Yes side.

Edge is the foundation of every serious trading strategy in prediction markets, sports betting and financial derivatives. Without an edge, you are paying transaction costs to take random risk.

Profitable traders look for situations where the market price disagrees with their model. That model might be a statistical forecast, an information advantage (a source close to the story, an obscure dataset), or a behavioural read (the market is over-reacting to a headline).

• Build an independent probability estimate before looking at the market price.
• Compare to the contract's implied probability using this calculator.
• If the edge is large enough to cover fees, slippage and your own error rate — consider sizing in.
• If the edge is small or negative, stay out. Most contracts are reasonably priced.

Expected value (EV) weights every possible outcome by its probability. For a Yes contract bought at 62¢ with your estimated 70% Yes probability and $100 risked, EV is: 0.70 × profit_if_yes + 0.30 × −$100. A positive number means the average outcome of repeating this bet many times is profitable.

The calculator does this math for you. Treat EV as a guide, not a guarantee — every estimate has error bars, and any single trade can lose your full premium.

Markets aggregate the opinions of every trader weighted by their capital. They are usually well-calibrated on visible events, but they can lag breaking news, over-react to narratives, or systematically misprice niche markets where capital is thin. That's where edge lives.

• A late-cycle election market where a new poll has moved the underlying probability but contract price hasn't caught up.
• An economic event (CPI print, Fed decision) where futures markets imply a different probability than the prediction market.
• A sports event contract where the equivalent sportsbook line implies a meaningfully different probability.

Most novices systematically over-estimate the probability of dramatic outcomes (a candidate winning from behind, a long-shot championship). The calculator helps you check yourself: if the market says 25% and you say 60%, ask whether you really have information the rest of the market lacks.

Forecasters like those tracked by Tetlock's Good Judgment Project rarely commit to round numbers. They think in ranges, update on new information, and stress-test their estimates. The most reliable trading edge in prediction markets comes from disciplined Bayesian updating, not from gut conviction.

• Anchoring on the headline price instead of building an independent estimate first.
• Treating a hot streak as evidence of skill.
• Forgetting that fees and slippage shrink your edge on every trade.
• Ignoring base rates — most things that have happened before will happen again at roughly the same rate.
• Over-sizing on a small edge. See the Position Size Calculator.

Event contracts are financial instruments. You can lose 100% of your premium. A positive estimated edge does not guarantee a winning trade and edges shrink in the presence of fees, slippage and liquidity constraints. Trade only where legally permitted in your jurisdiction. This tool is for educational purposes only — not investment, legal or tax advice.