PredictedProbability

Master Probabilities

Essential tools and calculators for prediction market traders. Understand implied probability, edge, and fair value.

Popular Calculators

Bayes Update

Update a prior probability with new evidence using a likelihood ratio.

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Break Even Probability

Find the minimum probability required to profit after fees.

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Edge vs Market Price

Calculate your theoretical edge and expected value against the market price.

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Odds Converter

Convert between Probability, Decimal Odds, Moneyline, and Log Odds.

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Price to Implied Probability

Convert a prediction market price into an implied probability percentage.

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Probability to Fair Price

Determine the fair trading price for a given probability belief.

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Latest Guides

Bid, Ask, Mid: Why Last Traded Price Is Misleading (Use This Instead)

Bid, Ask, Mid: Why Last Traded Price Is Misleading (Use This Instead)

Last traded price often looks like the market price, but in prediction markets it can be stale, tiny, or off the executable quotes. This guide explains why last trade misleads, what to use instead (bid, ask, mid, and order book depth), and how to avoid hidden execution costs.

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Effective Spread and Realized Spread: Measuring Execution After the Fill

Effective Spread and Realized Spread: Measuring Execution After the Fill

Quoted spreads are what you see. Effective and realized spread are what you actually paid. This guide explains effective spread vs realized spread, how to use mid price correctly, how price improvement shows up in the numbers, and why you must separate fees from microstructure costs.

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Settlement Rules: Where the Real Risk Hides

Settlement Rules: Where the Real Risk Hides

Execution costs are visible. Settlement risk is not. This guide explains how settlement rules and oracle design determine what you are really trading, how ambiguous outcomes create hidden risk, and a checklist for reading market rules like a professional.

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