Methodology

1. The formula is a tested function

Each calculator is a pure TypeScript function with no interface attached to it. It takes typed inputs in SI units, returns a structured result, and has a test file next to it. The tests cover known worked examples, zero, negative and empty input, very large and very small values, decimals, both unit systems, conversion round trips, invalid text and the edges of every allowed range. A calculator that does not pass its tests does not build.

2. The assumptions are on the page, not in the code

Every result carries the list of assumptions that produced it: the waste allowance, the bag yield used, the truck capacity, the unit weight, the rounding increment. They are printed under the takeoff and included in the CSV export. If a number surprises you, the reason is on the same screen.

3. Sources are documents, not vibes

Reference values, bag yields, unit weights, standard practice, are taken from published material by the organizations that publish it: ACI, the Portland Cement Association, NRMCA, and the manufacturers' own product data for their own products. The title block counts them and the page lists them with what each one was used for. Where a deep link is not stable we link the organization rather than invent a URL.

4. Practice is labelled as practice

Tables like "common slab thickness" describe what is ordinarily done in US residential construction. They are not code, they are not engineering, and they are labelled that way every time they appear. Your building department, your engineer and your drawings outrank anything on this site.

5. Sheets are versioned

Each calculator has a formula revision number and a revision date in its title block. The revision changes whenever the math or an assumption changes, not when a typo is fixed. Changes that alter a published result are listed on the corrections page.

6. Nothing is published before it works

The tool registry marks each sheet live, draft or planned. Only live sheets appear in the sitemap and only live sheets can be linked from a workflow rail, so a sheet that is still being drawn cannot leak into search results or produce a dead link. Planned sheets are listed, greyed, and not clickable.

7. The page works without JavaScript

Every calculator is rendered on the server with its default inputs: the form, the result, the takeoff table and both drawings are real HTML before any script runs. JavaScript makes it live; it is not required to read the answer.

8. What we do not do

• We do not publish national average prices. Prices are local and dated; the calculators take yours.
• We do not generate pages in bulk. Each sheet is written by hand for a job somebody actually does.
• We do not attribute content to engineers, inspectors or credentials we do not have.
• We do not load third-party scripts, trackers or fonts on a calculator page.