How we verify our calculators
Every calculator on CalcoTools is built from a real formula, standard, or — where the calculation depends on a fact rather than pure arithmetic — a source we actually read. This page is a category-level overview of what each part of the site is built on; for the exact formula and citation behind a specific finance or health tool, see How We Calculate. Every tool page also carries its own "last reviewed" date, which reflects that specific tool, not this overview.
This overview was last compiled and reviewed on September 5, 2026. We aim to re-review it quarterly. This date reflects when this page itself was checked against the site's actual tools — it isn't a claim that every individual tool was re-verified against its source on this exact date; check a tool's own page for that.
Built on standard textbook mathematics — geometry, algebra, and number-theory identities (area/volume formulas, GCF/LCM via the Euclidean algorithm, logarithms, and so on). These don't depend on an external fact that can go stale; correctness is verifiable by direct computation.
Built on standard Gregorian-calendar arithmetic and ISO 8601 date handling, using each visitor's own locale for display formatting.
Built on published rates and standard financial formulas — IRS brackets and rules for US tax tools, HMRC/CRA/ATO figures for UK/Canada/Australia tax tools we cover, and textbook amortization/compound-interest/annuity math for loans and savings. Full per-tool sources and formulas are in How We Calculate.
Built on named clinical/nutritional formulas and cited research where the calculation depends on a published fact — for example the Mifflin-St Jeor equation for BMR, the 2011 Compendium of Physical Activities for MET-based calorie estimates, and ACOG guidance for cycle/fertility-window tools. None of these are medical advice — see each tool's own disclaimer.
Built on published unit-conversion factors and standard definitions (NIST's reference constants for length/weight/volume conversions, SI/ISO unit definitions).
Built on language and specification-defined behavior — RFC 3986 for URL encoding, IEEE 754 for floating-point arithmetic, the Unix-epoch definition for timestamps. Where a tool cites a real-world fact instead (like current LLM API pricing), that fact carries its own dated source and a note to verify it's still current.
Runs entirely client-side (nothing you upload leaves your browser) using standard image-processing operations — no external factual claim to source.
Runs entirely client-side using standard document-processing libraries — no external factual claim to source.
Found a calculation, formula, or source that looks wrong? Email us directly at altheriontechnologies@gmail.com and we'll look into it — see the Help Center for other ways to reach us.