Editorial policy

We prefer primary sources: federal statistical agencies first, then official state and municipal data, then manufacturer specifications. Every dataset records its source, publication period, retrieval date, licence, and known limitations on the data sources page.

We do not copy proprietary cost tables, and we do not scrape any site in violation of its terms. Where a needed figure has no public source, we say so and label it an assumption rather than implying it was measured.

Presenting a single number for something genuinely uncertain is a form of inaccuracy. Every estimate here is a range with a confidence level, and every result states what the calculator could not know.

Where a modelling choice is contestable, we explain the choice rather than hiding it. The contractor burden multiplier is the clearest example: it is the largest lever in every project calculator, it is our judgement rather than a measurement, and we say so on the result itself.

Advertising has no influence on any figure, recommendation, or piece of guidance. No advertiser has input into calculator logic or content. We do not accept payment for favourable treatment, do not sell leads, and do not run affiliate links inside calculator results. See the advertising disclosure.

When we find or are shown an error, we fix it and record the change in the project changelog. Corrections that change results also bump the assumptions version, so an estimate can always be traced to the model that produced it.

Report problems through report incorrect data. Reports from people working in the relevant trade are especially valuable and are prioritised.

We publish estimates and explanatory guidance. We do not publish legal, financial, engineering, or trade advice, and we do not tell anyone whether to proceed with work. Any decision involving structure, wiring, gas, plumbing, or mechanical systems belongs with a licensed professional who has seen the property.

This site was built with substantial assistance from an AI system, working from public data sources and a documented specification. Being straightforward about that matters more than the marketing value of implying otherwise.

What that does not change: every statistic is traceable to a named source with a retrieval date, every assumption is labelled as an assumption, and every calculator is covered by automated tests that run on every change. What it does mean is that the material price baselines in particular deserve scrutiny from people who buy these materials for a living, and corrections are genuinely welcome.