Free tools for prediction-market edge
Probability math, Kelly sizing, slippage, fees, and live Polymarket workflow tools in one place.
Conversions
Translate odds, prices, and implied probabilities
EV & Sizing
Estimate edge, EV, Kelly, and bankroll exposure
Fees & Arbitrage
Stress-test fees, hedges, and bundle arbitrage
Execution
Walk the book before you cross the spread
Performance
Measure calibration and forecast quality
Workflow
Resolve slugs, token IDs, quotes, and positions
Trader workflows
Browse by market task before you search.
Conversions
Translate prices, odds, APR, and probability moves
EV & Sizing
Edge, EV, Kelly, bankroll, and take-profit math
Fees & Arbitrage
Bundle arbs, fees, hedges, and portfolio floor checks
Execution
Orderbook depth, slippage, spreads, and live liquidity
Performance
Brier, log loss, calibration, and reliability plots
Workflow
Slug parsing, metadata fetches, quotes, and positions
Featured tools
The core calculations traders bounce between all day.
Start with probability, edge, Kelly, and fees, then move into orderbook-aware tools once you have a live token in hand.
Implied Probability Converter
Convert a prediction-market price into implied probability in one step.
Price-from-Probability Target
Turn your belief into a fair price, rounded to a usable tick.
Probability to Logit Converter
Convert between probability and log-odds for Bayesian-style workflows.
Odds Converter
Convert American, decimal, or fractional odds into implied probability.
Conversions
Translate prices, odds, APR, and probability moves
Implied Probability Converter
Convert a prediction-market price into implied probability in one step.
Price-from-Probability Target
Turn your belief into a fair price, rounded to a usable tick.
Probability to Logit Converter
Convert between probability and log-odds for Bayesian-style workflows.
Odds Converter
Convert American, decimal, or fractional odds into implied probability.
Multi-Outcome Normalizer
Normalize a list of outcome prices into probabilities that sum to 100%.
Overround / Vig Estimator
Measure how far a set of implied probabilities sits above or below 100%.
Annualized Return Calculator
Compare hold-to-resolution opportunities across different expiries.
Target Price for Desired ROI
Find the highest price that still supports your expected ROI target.
Implied Probability Change
Express a market move as percentage points and basis points.
EV & Sizing
Edge, EV, Kelly, bankroll, and take-profit math
EV Calculator
Compute expected value per share and for a given stake size.
Edge Calculator
Measure the gap between your probability and the market's.
Kelly Bet Size
Estimate full-Kelly bankroll sizing for a binary share trade.
Fractional Kelly Sizer
Scale Kelly sizing down to a more survivable fraction.
CRRA Utility Bet Size
Optimize stake size for a chosen level of risk aversion.
Risk-of-Ruin Approximation
Estimate the chance of finishing below a ruin threshold over repeated bets.
DCA Weighted Average Entry
Combine multiple fills into one clean average entry price.
Break-Even Probability
Compute the minimum belief required to justify a price before fees.
Position Target Take-Profit Price
Find the exit price required to hit a target return.
Expected Log Growth Comparator
Compare two candidate trades by expected log growth, not raw EV alone.
Fees & Arbitrage
Bundle arbs, fees, hedges, and portfolio floor checks
Fee-Aware Break-Even Price
Solve for the maximum price that still breaks even after trading fees.
YES + NO Bundle Arbitrage ROI
Check whether buying both sides still locks in a positive resolution payout.
Cross-Platform Binary Arbitrage ROI
Check a buy-YES / buy-NO complement trade across two venues.
Hedge Size Calculator
Estimate how many opposite-side shares you need to cap downside.
Conditional Probability Calculator
Derive P(A|B) from a joint market and its conditioning event.
Implied Correlation Calculator
Estimate Bernoulli correlation from single-event and joint-event prices.
AND / OR Probability Combiner
Combine two beliefs under an explicit independence assumption.
Market Parity Checker
Check whether two related markets violate a simple logical relationship.
Portfolio Worst-Case Payout
Estimate the worst-case payout across a basket of YES and NO positions.
Portfolio Concentration Index
Quantify concentration risk with a Herfindahl-Hirschman score.
Polymarket Fee Calculator
Estimate taker fees from shares, price, and fee-rate assumptions, with token lookup support.
Execution
Orderbook depth, slippage, spreads, and live liquidity
Spread Cost Calculator
Quantify what you pay by crossing the bid-ask spread instead of trading at mid.
Tick-Size Rounding Helper
Round a raw limit price to the nearest valid tick increment.
Maker vs Taker Cost Comparator
Compare waiting passively versus crossing now after fees.
Execution-Adjusted Edge
Convert paper edge into net edge after spread and fees.
Orderbook Slippage Estimator
Walk the public orderbook to estimate average fill price for a marketable order.
VWAP from Orderbook
Compute VWAP for a hypothetical buy or sell size from current depth.
Liquidity-at-Price Snapshot
See how much size is available within a chosen slippage band from the top of book.
Orderbook Imbalance Indicator
Measure how bid-heavy or ask-heavy the top of book is right now.
Performance
Brier, log loss, calibration, and reliability plots
Brier Score Calculator
Score single predictions or batches of forecasts with Brier loss.
Log Loss Calculator
Evaluate forecast quality with ignorance score / log loss.
Brier Skill Score Calculator
Measure your Brier improvement versus a baseline forecast.
Calibration Error (ECE) Calculator
Estimate expected calibration error from a forecast log.
Sharpness (Entropy) Calculator
Measure how concentrated or timid your forecasts are on average.
Market vs Me Score Delta
Compare your forecasts against market-implied probabilities on the same resolved events.
Reliability Diagram Generator
Generate an SVG reliability plot from a batch of resolved forecasts.
Workflow
Slug parsing, metadata fetches, quotes, and positions
Polymarket URL to Slug Extractor
Pull the canonical event slug from a Polymarket URL.
Slug to Market Metadata Fetcher
Resolve a Polymarket slug into markets, token IDs, outcomes, prices, and end date.
Token ID to Live Best Bid / Ask
Fetch the current best bid, ask, spread, and midpoint for a token.
Token ID to Price History Downloader
Download recent Polymarket price history as CSV from the public CLOB feed.
Wallet to Positions Snapshot
Pull a wallet's current Polymarket positions and total marked value.
Keep momentum
Keep the math tight, then move straight into execution.
The directory is organized the way traders think: conversion first, edge second, execution third, and review after settlement. Each tool answers a single question cleanly enough to screenshot or share.
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Utilities
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Live-data tools