Free tools
Four small tools for people who trade prediction markets and crypto perpetuals. Each one does a single calculation properly, shows the formula it used, and says what the formula leaves out. They run entirely in your browser.
- Calculators
- 4
- Questions answered
- 16
- Reference guides
- 5
All three are counted from the pages themselves when the site is built: the calculators in the registry, the questions actually printed under each one, and the guides in the reference section. None of them is a usage figure. We do not publish numbers we have not measured, and we have never measured how many people open a calculator.
Who these are for
If you trade Polymarket and also carry perpetual futures, you switch between two number systems all day. One is quoted in probabilities between zero and one, the other in leverage, funding rates and liquidation distances. Nothing translates automatically between them, and the mental arithmetic is exactly the kind that goes wrong quietly.
These tools cover the four calculations that come up most often in that gap: what a price means as a probability, how much of a bankroll a position deserves, what it costs to hold a perpetual open, and how far the price has to move before the position is closed for you. None of them needs an account, a subscription, or a network connection once the page has loaded.
They are also a fair sample of how EdgeMarket works. Every assumption is a field you can change rather than a constant buried in the code, every output that cannot be computed shows a dash instead of a plausible-looking zero, and every page explains the formula rather than asking you to trust it.
The tools
Prediction markets
Odds converter
Convert odds to probability and back — decimal, American, fractional and percentage — and pull the vig out of a two-sided market.
Answers: what probability is this price actually quoting, what are those odds as a percentage, and what is left after the spread?
Open this calculator
Position sizing
Kelly position size calculator
What the Kelly formula says to stake on a stated edge — and why full Kelly is almost never the right answer.
Answers: how much of the bankroll does this edge justify, and what does that size cost in drawdown?
Open this calculator
Crypto perpetuals
Funding cost calculator
What a perpetual futures position costs to hold while a thesis plays out, per funding interval and per day.
Answers: what does this position cost per day, and how much of that is the settlement interval rather than the rate?
Open this calculator
Risk
Liquidation price calculator
Find where a leveraged position gets closed for you, how far that is in percent, and how much adding margin actually moves it.
Answers: how far can the price go against this position before the venue closes it?
Open this calculator
How these are built
Four constraints, chosen because they are what makes a calculator worth bookmarking rather than worth opening once.
- Everything is computed in your browser. No values are sent anywhere, nothing is logged, and the page keeps working with the network switched off.
- Every input lives in the address bar. Copy the link and you have copied the whole calculation, which makes these tools usable in a message, a ticket, or a note to yourself.
- Assumptions are inputs. Maintenance margin rates and funding intervals differ by venue and by contract, so they are editable fields with a labelled default, never a hard-coded constant presented as fact.
- Each page writes out the formula and its limits. A calculator you cannot audit is a calculator you cannot use for anything that matters.
Which tool for which job
The calculators above are ours. The rest of the Polymarket toolset is not, and picking between a whale tracker, a leaderboard and a research tool is easier with them side by side.
- Best Polymarket analytics tools
Most of these tools show you the same trades. What separates them is what they decide is worth showing, and whether they let you check the decision afterwards.
- Polymarket whale tracker
A large trade and an important trade are not the same event. This tracker is built to tell them apart.
- Crypto prediction signals
Anyone can publish the calls that worked. The only number worth reading is the one that includes the ones that did not.
- Polymarket tools
Four things decide most prediction-market outcomes, and only one of them is the forecast.
- How to track whale trades on Polymarket
The data is public and free. What costs something is deciding which of ten thousand trades deserved your attention.
- A PolymarketScan alternative
PolymarketScan tells you a large trade happened. The question this page answers is what you would want next to it.
- A Polywhaler alternative
Polywhaler does one thing and does not pretend otherwise. Whether that is a virtue depends on what you do with the alert.
The mechanics behind the arithmetic
A calculator returns a number. It does not tell you what the number is measuring, and that is the part which decides whether the number is worth anything. The reference guides take one mechanism each — what a share priced between zero and one actually is, what a funding payment settles, how a liquidation engine behaves when the book thins out — and explain it in full, under the same rule as the rest of the site: no figure appears unless it has been measured, and the parts that do not flatter us are printed next to the parts that do.
Where the numbers on the rest of the site come from
These calculators take their inputs from you. The statistics EdgeMarket publishes elsewhere are measured on our own data and shown with the slices that do not flatter us, including the share of slots we could not verify at all. If you want to judge whether the rest of the site is worth reading, that page is the place to start.