How we build calculators you can trust

A calculator that hands you a number and hides the method asks for blind trust. We would rather earn it.

On every tool, the formula, the standard it follows, and the meaning of each input are written on the page. That serves two purposes. First, you can sanity-check the result against your own knowledge instead of assuming the machine is right. Second, you learn something — the page explains why the answer is what it is, not just what it is.

This philosophy also keeps us honest. When the method has to be visible, there is nowhere to hide a lazy shortcut or an unsupported rule of thumb.

We do not invent formulas. Each calculator is built on an established, published method — the kind used in textbooks, standards documents, peer-reviewed research or official guidance. Our job is to implement that method faithfully and explain it clearly.

We prefer sources in roughly this order:

1. Official standards and regulations — for example, national and international engineering or safety standards that define how something must be measured.
2. Peer-reviewed research and academic references — for formulas that originate in published studies or established science.
3. Recognised institutional guidance — health, financial or professional bodies that publish accepted methods and thresholds.
4. Widely used, well-documented conventions — where a field has settled on a standard approach even without a single governing body.

Every tool goes through the same disciplined path from idea to published page.

Testing is where a calculator earns its keep. We check two different things: that the maths is right, and that the page works for a real person on a real device.

Checking the maths

Before a tool is published, its outputs are compared against independent reference points — worked examples from the source material, published reference tables, and hand calculations. For the aquarium glass calculator, for instance, the recommended thickness for standard tank sizes was checked against an established reference table until the two agreed. A tool only ships once its numbers line up with these known-good values.

Checking the page

We then load the finished page in a genuine browser — not just a quick preview — and drive it the way a visitor would: change inputs, switch options, resize to a phone screen, and confirm there are no errors, no broken layout and no sideways scrolling. This catches the practical problems that pure maths checks miss.

No calculator captures every real-world variable, and pretending otherwise would be dishonest. Where a tool relies on an assumption or cannot see the full picture, the page says so directly.

• Simplifying assumptions are stated. If a result assumes, say, a full water column or a particular rounding rule, that assumption is written on the page.
• Ranges and thresholds are explained, not just coloured. A "healthy" or "safe" band always comes with a note on what it means and where it comes from.
• We flag when a professional is the right call. For anything with real safety, legal, medical or financial stakes, the tool points you to qualified advice rather than posing as a substitute for it.

Our disclaimer sets out these limits in full.

We take accuracy seriously, and we treat a reported error as a gift rather than a complaint. If you believe a result is wrong, tell us — include the tool, the inputs you used, the number you got and the number you expected, and we will investigate.

When we confirm a genuine error, our bias is simple: fix it, do not defend it. Corrections to the underlying formula are prioritised, and most ship within days. If a fix materially changes results, we note what changed so returning users are not caught out.

The library is actively maintained. We add new calculators, refine existing ones, improve explanations and update figures when the underlying standards or rates change. Behind the scenes, each update is versioned so that everyone is served the current, corrected code rather than a stale copy.

If you rely on a specific result for an important decision, it is always worth re-checking the tool at the time you need it, since methods and figures can be refined between visits.