How We Write and Check Our Pages

Engineer Underground is a free library of guides, calculators and converters for engineers, makers and students. People rely on numbers from sites like this one, so this page says plainly how our pages are made and checked, and what to do when something is wrong.

Who is behind the site

Engineer Underground is operated by Engineer Underground, LLC, in the Phoenix, Arizona area. It was started by Nick Peterson, a mechanical engineer with a background in product development, automation and prototyping (about us). You can reach us from the Contact page.

How a page is made

• Plan. We choose topics that engineers and makers actually need, from everyday questions such as bolt torque, fits and tolerances, wire sizing or PLC wiring, and from the suggestions people send us.
• Research. We start from published standards, handbooks and manufacturer data wherever we can. Sources are listed at the end of the page, and where values differ between sources we say so.
• Write. Each guide explains the idea, gives the formula, and works one example all the way through with units. Values that vary by supplier, material grade or region are labeled “typical”, and the page tells you to use the data sheet or standard for your own work.
• Check. Every worked example is calculated independently, and each calculator is tested against the worked example on its own page and against hand-calculated values before it is published. Tables and constants are compared with the published sources.
• Review date. Pages carry a “last reviewed” line, and we update it when we revisit a page.

We use software tools, including AI-based research and writing assistants, to help research, draft and format pages. Nothing is published on the strength of a tool alone: the formulas, tables and worked numbers are checked by calculation and against the published sources, as described above.

What the numbers are, and are not

Our guides and calculators are for learning and for first estimates. They are not professional engineering, electrical, structural or safety advice, and they do not replace the standards, codes and licensed professionals your work requires. Please check any result that matters before relying on it. The Terms of Service say this in more detail.

Corrections

If you find a mistake, tell us: use the “Was this page helpful?” note at the bottom of any guide or tool, or the Contact page. We read every report, correct confirmed errors, and update the page’s review date. If a correction changes a result you may have used, we say so on the page.

How the site is paid for

The guides, calculators and converters are free to read and use. The site is supported by advertising, and by optional paid memberships and a small store. Ads never decide what a guide says: pages are written first, and advertising is added around them. See the Privacy Policy for how advertising and analytics use data.