How Kalkuleyt calculators work
Every calculator on kalkuleyt is built from a documented formula or a named data source. This page explains how results are produced, how sources are handled, and where the limits of each tool are described.
How calculators are classified
Each calculator belongs to one method category shown in its Methodology & data section: deterministic math and unit conversion, financial and business arithmetic, external reference data, jurisdiction-sensitive arithmetic, health screening and energy estimation, and scientific or engineering formulas. The category tells you what kind of evidence a result depends on.
Formulas and sources
Formula-based calculators use standard, established formulas, and the formula is printed on the page so you can check the arithmetic yourself. Where an external source is needed (for example the international pound definition or a clinical screening equation), the source is named and linked in the same section.
No citation is invented and no source is attached to a page that does not use it.
Live data
The currency converter uses daily reference rates published by the European Central Bank via frankfurter.dev. The provider and rate date are displayed with each result. If rates cannot be fetched, the calculator reports that instead of showing a stale number.
Jurisdiction-sensitive calculations
VAT, sales tax, income tax and paycheck calculators use the rate you enter; they do not claim to know current country rules. Rates and thresholds change and depend on personal circumstances, so confirm results with the relevant tax authority or a qualified professional before relying on them.
Health calculations
BMI, body-fat, ideal-weight, calorie, BMR, macro, pregnancy and cycle calculators are adult screening or estimation tools. They are not diagnostic devices and are not a substitute for medical advice. Each page lists its assumptions and limitations.
Rounding and testing
Conversions use exact definitions where they exist, and rounding is applied only to what is displayed; a calculator cannot add precision that was not in the input. Calculation logic is covered by automated tests, and results are deterministic: the same input always produces the same output.
If a result looks wrong, the corrections policy explains how to report it.