This page describes how we choose sources, write results and handle mistakes and money. It applies to every calculator and every guide on the site.
Sources
We prefer, in this order: the manufacturer’s own published figures, trade associations, and university extension services. Where a figure comes from a manufacturer it is the figure for a named product or standard size, and we say so. Each source is dated when we check it, and the methodology page lists them all with their review dates. We do not copy another calculator’s output as a source.
Estimates and advice
We keep estimating separate from engineering advice. A calculator tells you how much material a stated job is likely to need. It does not tell you what thickness, mix, spacing or fixing a job requires. Where a guide touches on structural or safety matters, it points you to local codes and the product instructions instead of giving a rule of its own.
Corrections
If a result or a source is wrong, we fix it, record the change with its date in the corrections log on the methodology page, and say what changed. We do not quietly edit a number. To report a problem, use the contact page. Include the calculator, the inputs you used and the result you expected.
Authors and reviewers
When a page names an author or a reviewer, that is a real person who did the work. We do not invent bylines, credentials or testimonials.
Ads and affiliate links
The site may show ads served by Google AdSense. Ads do not influence a result, a default or the order in which we list tools, and we do not accept payment to change a number. Ads are never placed inside the calculator itself. If we add affiliate links, for example to a product we mention, each one will be marked clearly on the page where it appears. The privacy page explains what ads mean for your data.
Independence
No manufacturer or retailer pays for placement in our results. Where a calculator offers bag sizes or sheet sizes, it offers the common ones so that you can match what your supplier sells.