About CheckedCalc
CheckedCalc is a set of free engineering calculators for mechanical and aerospace design engineers in the UK and the US. Each tool is built so you can check it by hand. It shows the method, the standard it follows and the working behind every number.
Who it is for
It is for design engineers, stress engineers and technicians who need a quick, traceable answer during design work: a tolerance stack, a cylinder size, a press fit or a bolt torque. The pages assume you know the engineering and want a tool you can audit.
Why it exists
Most free calculators give a number without the formula, the edition of the standard or the assumptions behind it. That is not enough for a design review. A practising design engineer started CheckedCalc to get tools that can be attached to a design record and defended in front of a checker.
How each calculator is built and checked
| Step | What happens |
|---|---|
| Source | The method is taken from the governing standard first, then from recognised textbooks and papers. Each is cited with its edition. |
| Worked example | Every function in the calculation engine is checked against a worked example with a hand-checkable number from a cited source. |
| Automated tests | 903 automated tests cover the engines, units, reports and shared links. A change is published only when every test passes. |
| Technical review | The editor reviews the method, the assumptions and the copy before a page goes live. |
| Show the working | Each result can be expanded to show the formulas with your values substituted, so you can check it by hand. |
| Report | Inputs, method, results, assumptions and standards in one printable record. |
Every worked example and its computed value is listed on the validation page.
Units and scope
SI units come first, with inches on request. One unit system is used per calculation and converted only at input and output. Each page states where its method stops being valid.
Who writes it
The calculators are written and reviewed by The CheckedCalc editor, a mechanical design engineer. See the editor page, the editorial policy and the terms of use. Results are for evaluation and must be verified by a competent engineer before use in a design.