About Neutron STEM Lab

Neutron STEM Lab is a free collection of 66 engineering and science tools covering 12 subject areas. Everything runs in your browser, nothing requires an account, and no calculation you enter leaves your device.

Who builds this

Neutron STEM Lab is published by Neutron Studios LLC. The tools are built and maintained by the studio’s founding engineer.

Neutron Studios LLC is a small independent studio rather than a large publisher or a university department. The same engineer writes the calculation engines, the interfaces, the documentation, and the test suites, which means responsibility for anything wrong here sits in one place. If you find an error, it goes straight to the person who can fix it.

Why this exists

This started from a straightforward frustration: the tools I wanted while I was studying engineering did not exist in a form I could actually use. The good software was expensive, licensed to a university lab, or locked behind a seat I lost access to after graduation. The free options were usually a single formula in a box, with no indication of what assumptions were baked in or when the method stopped being valid.

So the goal here is the toolset I wish I had had as a student: something you can open in a browser during a problem set, that shows the intermediate quantities rather than just a final number, and that states plainly what it assumes and where it breaks down. A calculator that returns 4.72 without telling you it assumed fully developed turbulent flow has not taught you anything.

It is free because a paywall between a student and a bearing-capacity calculation is a bad trade. Engineering education is expensive enough already. Nobody should have to choose between checking their work and affording a licence, so there are no accounts, no trials, no feature tiers, and no "upgrade to see the full result."

How the tools are built and checked

Each tool separates its calculation engine from its interface. The engines are plain functions, which makes them testable in isolation, and they are covered by an automated test suite that checks results against worked values from standard engineering and physics references rather than against the code's own output. Textbook cases with known answers are the yardstick: a second-order system at a damping ratio of 0.5 must overshoot by 16.3%, the speed of sound in air at 20 °C must come out at 343.2 m/s, and so on.

Every tool page publishes the governing equations, the assumptions the implementation relies on, the limitations that follow from them, and the references used. That material is not decoration. If a tool assumes Rankine earth pressure with a smooth vertical wall, or a calorically perfect gas with a constant specific heat ratio, that is stated, because knowing when a result does not apply matters more than the result itself.

Alongside the engine tests, a set of repository verification scripts runs on every change. They check that each tool has documented equations, assumptions, limitations and references, that graphs carry labelled axes with units, that inputs are bounded to physically sensible ranges, and that the published catalogue matches what actually ships.

The full methodology, including how sources are chosen and how validation status is reported, is on the calculation and validation methodology page.

Published tools and engineering validation

Tools in the public directory are published for normal use; software publication is kept separate from engineering-validation coverage. A working interface does not become more trustworthy merely because it carries a maturity badge, so public tool cards do not use beta or stable labels as a substitute for evidence.

Instead, each workbench reports the evidence that is actually published: documented equations, assumptions, limitations, and references, plus representative validation cases, worked examples, and editorial review dates when those materials are available. Software lifecycle labels are not used as a substitute for engineering evidence.

How this is paid for

The site is free to use and is intended to be supported by advertising so the engineering tools can remain available without accounts, subscriptions, or feature paywalls. Advertising never influences which methods are implemented, what a calculation returns, or what the assumptions and limitations sections say. There is no sponsored placement inside a result, and no engineering content is written to suit an advertiser. How advertising and analytics handle data is described on the privacy page.

Corrections

If a result looks wrong, please report it. Engineering calculations are falsifiable, so a specific report — the tool, the inputs you used, the value you expected, and the source you are comparing against — is usually enough to confirm or rule out a problem quickly. Corrections to a calculation engine are treated as the highest priority category of change on the site, ahead of new tools and new features.

Reports go through the contact form, which has a dedicated "Report an incorrect result" topic. Fixes ship with a regression test covering the reported case, so the same error cannot return unnoticed.

What this site is not

These tools are for learning, checking work, and early-stage estimation. They are not a substitute for design software used under a quality system, for the governing code or standard in your jurisdiction, or for review by a licensed professional engineer. Nothing here is stamped, certified, or suitable as the sole basis for a decision that affects safety. The engineering disclaimer sets out the limits in full.

Last reviewed: 2026-08-11