How We Build and Check Our Calculators

Most flooring calculators online are a coverage formula in a box, with no way to tell where the numbers came from or whether anyone checks them. If you are about to order thousands of dollars of resin, or send a client a fixed price, that is not good enough.

This page sets out how Trade Epoxy tools are built, which figures are computed rather than typed in by hand, and what runs automatically every time we ship a change. It also says plainly where our numbers stop and your product data sheet takes over.

Trade Epoxy is built by a small team working with practising epoxy and concrete flooring contractors. The tools come out of real jobs: quoting a garage floor, sizing a flake system, working out whether a grind is priced to make money.

We publish under the Trade Epoxy name rather than a personal byline. Nothing on the site is attributed to an invented expert, a stock photo persona, or a set of credentials we do not hold. If a figure on this site is right, it is because it was checked, not because someone signed it.

Every calculator carries a Feedback button. Corrections from working contractors are the main way these tools improve, and several calculators exist because someone asked for them.

Each calculator draws on one of three kinds of input, and we keep them separate on purpose:

• Your inputs. Area, film build, product coverage rate, crew size, hourly rate. Anything specific to your job or your business is something you enter, never something we assume.
• Industry standard reference values. Published coverage rates, typical grinding production rates by pass, grit sequences, cure and recoat windows. These are starting points that match how the trade actually works, and every one of them is editable where the product varies.
• Arithmetic we can defend. Waste allowances applied before kit round up, overhead spread across billable days, margin applied as margin rather than markup. The order of operations in a quote changes the answer, so we pin it.

Prices are the one thing we will not invent. Material costs, labour rates and machine rates are yours to enter, because they move by region, supplier and week. Where a calculator needs a rate to work, it asks for it rather than guessing on your behalf.

The honest answer to "how do you know these numbers are right" is that the site refuses to build if they are not. Four automated checks run against the real code, not against a copy of it:

• Pricing engine: 212 checks across 8 hand calculated fixtures. Each fixture is a complete job priced by hand first, then priced again by the live engine, and the two have to agree to the cent. Three of them are real quality assurance estimates taken from actual jobs. The set also covers the invariants that quietly break: changing the machine count changes the duration but not the money, waste percentage applies before kit round up, and the same physical floor costs the same whether it was entered in square feet or square metres.
• Published hour figures: 18 checks across 3 pages. The polished concrete guides print specific labour hours for a 1000 square foot floor. Those hours are not written down anywhere. They are outputs of the live polish engine, and the check recomputes all four of them and fails if the published prose has drifted. It also pins what the prose derives from them, including the cost per square foot and the widths of the bars in the chart.
• Quote documents: 24 checks. Pro quotes render as real PDFs, then get read back and inspected. The client facing quote is checked to confirm it carries none of your internal cost figures, and each of those figures is confirmed present on the internal document first, so a renamed label fails loudly instead of quietly weakening the check.
• Page copy. A style gate parses the prose on every guide and calculator page and fails the build on house style breaches, so wording stays consistent across the whole site as it grows.

Each of those checks is itself calibrated. Before a check is trusted, it is proved that it can still detect the fault it exists to catch. The hour check was proved by deliberately changing a production rate in the engine: it reported nine mismatches across four published surfaces, then reported none once the change was reverted. A check that always passes is worse than no check, because it reads as evidence.

The failure mode we design against is not a wrong calculator. It is a right calculator sitting next to a paragraph that was written when the calculator worked differently.

So where a guide quotes a number that the tools can produce, that number is treated as an engine output and tied back to the engine by a check. If someone tunes a production rate, the guide that quoted the old figure breaks the build rather than silently becoming untrue. It is a small discipline that stops the written pages and the working tools drifting apart over months.

This matters more than anything else on the page. Every result is an estimate based on the values you entered and the reference rates described above. Coverage, pot life, recoat windows and cure times vary by product, batch, substrate, temperature, humidity and technique.

Before you order material or start applying it, confirm the critical figures against the manufacturer's Technical Data Sheet for the exact product you are using. Where a TDS and a Trade Epoxy default disagree, the TDS wins, and the calculator is built to let you type the TDS value straight in. Our disclaimer covers the full position.

Some numbers are left out on purpose, and it is worth saying which:

• Made up market rates. Contractors regularly ask what the going rate is for concrete grinding. We do not publish one, because we do not have a defensible source for it. A confident number with nothing behind it is the most damaging thing a pricing site can print, because people quote against it.
• Invented prices in worked examples. Where an example needs a price, it is labelled as an example input, not presented as what things cost.
• Fabricated authority. No invented author credentials, no unearned certifications, no press logos we have not actually appeared in.

When we do not know something, the honest answer is to leave the gap visible rather than fill it.

The "Last updated" date on a page is the date that page's content actually changed, taken from the project's own revision history. It is not the date the site was last deployed, and it does not move because an unrelated page was edited. A date that quietly updates itself tells you nothing, so ours is wired to the content and nothing else.

Tell us. Use the Feedback button on any page, or the contact page, and say which calculator and which figure. Reports that include the product and the numbers you expected get fixed fastest.

You can also read more about what Trade Epoxy is, browse the guides, or go straight to the calculators.