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Methodology and editorial process

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1. Choosing what to build

We build a calculator only when it solves a real engineering or construction task and we can explain its method with reliable sources. If a result depends mainly on local codes, project conditions or tables we cannot cite, we do not publish a general calculator for it.

2. Written specification

Each calculator starts as a specification: inputs and units, valid ranges, formulas, assumptions, limits, test cases and the sources behind every formula, coefficient and table, with the edition and the clause or table number.

3. Building

The calculation code is shared across calculators and tested on its own. The default answer, tables and charts on each page are produced by the same code that runs the calculator, so the page text and the calculator always agree.

4. Separate recalculation and source checks

Before release, a verification step that is separate from the build recalculates the test cases, checks every table value and chart point against its source, and looks for any statement the sources do not support.

5. Automatic tests

Every change runs automatic checks: known-answer tests, unit conversions, rejection of invalid inputs, identical results with and without JavaScript, layout on small phones, accessibility, and checks that pages carry their sources and limitations.

6. Frozen results

Once a calculator is released, its test results are frozen. Any change to a formula, conversion or approved number is treated as a technical change. It must be recalculated and checked again before it goes live.

7. Versions and dates

Each calculator page shows its method version and the date of its last technical update.

What a published calculator means

A published calculator has been checked against its stated method, conditions and referenced sources. It is not a design for your project, not a certification or professional seal, and not an approval for every jurisdiction.

Corrections

If you find an error, please tell us through the contact page with the inputs you used. We check every report, fix confirmed errors and update the method version and date on the page.