Calculators you can check, not just read

Each calculator is a single page with three parts: the inputs, a worked example with real numbers, and a short explanation of the method. Category pages group the tools by subject, and the full calculator index lists everything with a one-line description. Calculators can also be embedded on other sites; embedded copies are marked noindex and are not treated as separate pages in search.

There is no paywall, no sign-up, and no advertising script on the site today. Saving a result writes a summary to your own browser storage, not to a server.

Total Calculation is built and operated by 44Tag Studios, a graphic and web design studio in Johannesburg, South Africa. The studio designs, builds, and maintains this site, so there is no bank, brokerage, clinic, or software vendor behind the results and nothing is being sold through them.

The publisher is accountable for corrections, complaints, and legal notices at 44tagstudios@gmail.com or +27 69 494 4349. Studio work and client references live at 44tagstudios.co.za.

Calculators use closed-form formulas or published equations rather than fitted guesses, and each page documents the one it applies. Representative examples:

• Compound growth: FV = P × (1 + r/n)^(n×t), plus the standard annuity term for recurring contributions.
• Fixed-rate loans: the amortisation payment M = P × r × (1 + r)^n / ((1 + r)^n − 1), with a separate schedule for principal and interest.
• Basal metabolism: the Mifflin-St Jeor equation (10 × kg + 6.25 × cm − 5 × age ± adjustment).
• Body composition: the U.S. Navy tape method using waist, neck, hip, and height.
• Strength estimates: the Epley formula 1RM = weight × (1 + reps / 30).
• Unit conversions: exact defined factors, e.g. 1 inch = 2.54 cm and 1 US gallon = 3.785411784 L.

Where a model is inherently approximate — body-fat tape methods, calorie burn estimates, material waste allowances, or fuel consumption on a real route — the page says so and shows the assumed inputs instead of presenting a single number as certainty.

Four checks run against the repository. The catalogue audit and the prerender audit are wired into the build itself; the formula tests and the TypeScript check are run before a change is published. A change is only considered done when all four pass:

• Catalogue audit — rejects entries missing an introduction, method explanation, worked example, at least three FAQs, valid related links, or SEO metadata.
• Formula tests — unit tests assert known results for the shared calculation modules (loans and amortisation, compound interest, mortgage payments, fuel-cost data, unit and health formulas, and catalogue config formulas).
• Type check — the whole project compiles under TypeScript with no errors.
• Prerender audit — inspects every generated HTML page for a unique title and description, a self-referencing canonical, matching Open Graph URLs, correct robots directives, and a sitemap entry.

Coverage is uneven by design at this stage: shared libraries and high-traffic finance calculators have dedicated tests, while some simpler converters are covered only by the catalogue audit and manual checks. A passing build means the checked properties hold — it does not mean every number on every page has been independently reviewed.

Most calculators need no external data. The exceptions are handled explicitly:

• South African fuel prices — taken from the Department of Mineral and Petroleum Resources monthly schedule, shown with the schedule's effective date and the date the figures were last checked. Diesel is labelled as a wholesale baseline because it is not a regulated pump price. Until a new schedule is published, the next adjustment date is shown as pending rather than filled in with an estimate.
• Currency rates — reference rates from open.er-api.com, timestamped on the page. They are indicative mid-market rates, not the rate a bank or card issuer will apply.
• Conversion factors — defined constants (SI and customary definitions) rather than measured values, so they do not go stale.

Figures that change on a schedule are stored in a versioned data module with their effective date, the date they were verified, and their source, so an outdated figure can be identified and replaced in one place instead of being retyped across pages.

If a result looks wrong, email the address on the Contact page with the calculator name, the inputs you used, the result you saw, and the result you expected. A worked correction is more useful than a description, and it is the fastest way to get a fix verified.

Reports are read, but this site does not promise a response time or a service-level agreement, and it is not a support channel for a bank, lender, employer, or clinician. Corrections that change a published result are made in the calculator and its worked example together, so the page never contradicts itself.