Prediction-market calculators
The arithmetic, free, with the assumptions written down.
Every one of these runs entirely in your browser. Nothing is sent anywhere, nothing is stored, no account, no email. They exist because the numbers that decide a trade — the all-in price after fees, the fair price with the margin out, the size, the cost of the wait — are arithmetic, and arithmetic should not be behind a signup form.
The calculators
- Implied Probability Calculator
A price is a probability wearing a costume. - No-Vig Fair Odds Calculator
Both sides added together tell you what the market is charging you to be there. - Polymarket Fee Calculator
The fee is not a percentage of your stake. It is a curve, and it peaks where you trade most. - Kelly Criterion Calculator
A sizing rule for an edge you already have. It cannot give you one. - Resolution Time-Value Calculator
A 95¢ contract is not a 5% trade. It is a 5% trade divided by however long you have to wait for it.
Read the ideas behind them
- What is smart money in prediction markets
- How Polymarket fees work
- Implied probability explained
- Why P&L leaderboards lie
- Removing the vig
- What is edge in prediction markets
- Kelly criterion for prediction markets
- How Polymarket markets resolve
- Maker vs taker on Polymarket
- How to read a Polymarket wallet
- Prediction markets vs sportsbooks
- What makes a track record real
Read your own record
These price a trade. The free wallet X-Ray reads a whole history: paste any public Polymarket address and it returns the realised record, the percentile against the field and the most expensive habit in it. Free, permanently.
The record is free. The calls, while they are still open, are $12 a week or $49 a month.
Everything that has resolved is on the ledger for nothing, permanently, no account. What you pay for is time: the call at the moment the rule fires, at the price it fired at, on your own live page.
See what it costs →