Anyone sizing a shaft or verifying a bolted joint eventually puts the result into documentation. At that point it does not matter how a calculator looks, but whether its numbers are right and whether it is clear what it does and does not cover. This page answers both.
Where the formulas come from
Every calculator follows a named source: a standard, a guideline or a reference work of German engineering literature. Most frequently cited are Dubbel (Taschenbuch für den Maschinenbau), Böge (Technische Mechanik und Formeln), Roloff/Matek (Maschinenelemente), Gross (Technische Mechanik) and the Tabellenbuch Metall, together with Niemann, Decker, Haberhauer and Boeckh for heat transfer.
For the standards-based calculators the standard is named on the respective page - DIN 743 for shaft verification, ISO 6336 for gear load capacity, VDI 2230 for bolted joints, EN 1993 for structural steelwork, DIN 6892 for parallel keys, ISO 286 for fits, or AIAG and VDA 5 for measurement system analysis. The edition used is noted in the calculator.
How results are verified
Typing in formulas is not enough. The usual mistake is not in the equation but in a unit, a sign, or a special case at the edge of the valid range. Every calculator is therefore checked against a worked example from the literature: inputs as printed in the book, result must match to the digits given there. These checks are recorded and repeated on every change - currently 231 calculation documents.
When a new calculator is built
A calculator is only built if all three conditions are met:
- There is an application and a demand for it.
- No good tool for it exists on the internet yet.
- A worked example from the literature is available to verify the result against.
Where the limits are
The calculators are design aids and guidance for preliminary sizing. They replace neither review by a professionally qualified person nor a certified design. Where a method ends is stated in the calculator itself: the flange calculator covers stage 1 per EN 1092-1 and AD 2000-B7 and states that the full verification per EN 1591-1 is not included. The pressure vessel calculator gives basic stresses and a first wall thickness, not a design per AD 2000 or EN 13445.
What the verification PDFs contain
The export contains inputs, intermediate values, result and the basis used, so the calculation remains traceable even when the document later ends up with someone else. See pricing.