Methodology

How ProbabilityKit's calculators are built, what formulas they use, and how we keep the results trustworthy.

Everything runs in your browser

Each tool is implemented in plain JavaScript that executes on your device. There is no server-side computation, so your inputs never travel over the network. This is both a privacy choice and a performance one — results are instant and work offline once the page has loaded.

Formulas are shown, not hidden

Every calculator page states the formula it uses. For example, the odds converter routes all formats through decimal odds:

and the Kelly calculator uses the standard growth-optimal fraction:

We prefer this openness because a calculator you can't check is a calculator you can't trust.

Rounding and precision

Calculations are performed at full floating-point precision and only the displayed value is rounded, typically to two to four decimal places depending on the tool. Fractions (for example in the odds converter) are approximated to the nearest clean denominator, so a value like 91/100 may appear where a bookmaker would print a rounded traditional fraction.

How results are checked

Each formula is verified against worked examples and round-trip tests — for instance, converting decimal → American → decimal should return the original value. We also cross-check outputs against established references for the standard cases.

Limitations

The tools compute exactly what their formulas describe. They cannot account for information they aren't given — for example, the Kelly calculator assumes your probability estimate is correct, and the two-event probability results assume independence. Where an assumption matters, the tool says so on the page.

Corrections

If you find a genuine error, please tell us. We treat correctness as the whole point of the site and will fix confirmed mistakes promptly.