Methodology

Why we publish a methodology

A calculator is only useful if you can trust the number it returns. Many calculator sites hide the formula and ask you to accept the result on faith. Vanta Calc does the opposite: every calculator page should show the formula, the assumptions, and at least one worked example. This page describes the editorial process that sits behind those pages.

How we source formulas

For each calculator, we try to use a single authoritative source and cite it on the page. Examples:

• Finance: standard amortisation, time-value-of- money, and compound-interest formulas. Where local tax law applies, we cite the relevant authority (for example SARS for South African PAYE, transfer duty and VAT).
• Health and fitness: public references such as CDC, WHO, or NIH for BMI ranges, BMR equations, calorie multipliers, and similar. We disclose which equation we use (e.g. Mifflin-St Jeor versus Harris-Benedict for BMR).
• Construction and engineering: textbook formulas, with units stated explicitly (metric and imperial where relevant).
• Math and conversions: textbook identities and SI-derived conversion factors.

How we handle precision

Floating-point arithmetic in JavaScript is famously sloppy (0.1 + 0.2 is not 0.3). For any calculator where small errors compound — long mortgage schedules, retirement projections, compound interest over decades — we use Decimal.js(opens in new tab) with 50 digits of precision under the hood. The displayed result is rounded to a sensible number of significant figures for the domain.

What "last reviewed" means

Each calculator page carries a "last reviewed" date. On that date, a maintainer:

• Re-checked that the formula matches the cited source
• Verified that any time-sensitive rates (tax bands, prime rate, contribution limits) match the latest published values
• Ran the worked example end-to-end
• Ran the calculator against at least one external source

If the "last reviewed" date is older than a tax year or regulatory change you know about, please report it via the Contact page.

Limitations and disclaimers

Vanta Calcprovides general estimates, not professional advice. Financial calculators ignore fees, taxes, and product-specific terms unless explicitly stated. Health calculators are not a substitute for clinical advice. Always check the assumptions block on each calculator page — that is where we call out what is and isn't included.

For any decision with material financial, legal, or medical consequence, consult a qualified professional.

Reporting an error

We treat formula bugs as P0. If you spot one, see the Contact page — email or open a GitHub issue. Public reports get a faster response than private ones because the discussion stays trackable.