Editorial & Calculation Standards
Last updated: 30 September 2026
This page sets out the principles Numerila's tools are built to, in plain language. It is written for anyone using the site, not for developers.
Established methods, not invented ones
Every tool uses a standard, well-established formula or method for its subject. Nothing on Numerila uses a private or invented calculation. Where a subject genuinely has more than one legitimate convention (for example, how a statistics tool splits quartiles, or how a rounding tie is resolved), the tool states plainly which convention it follows and does not claim other conventions are wrong.
Authoritative sources
Where a tool depends on an external standard or reference figure, it cites the source by name. The Adult BMI Calculator's category thresholds follow the World Health Organization's global adult classification, with practical cautions drawn from current NHS guidance. The Currency Converter uses reference rates from Frankfurter, an independent exchange rate data service, and shows the date the provider gives for each rate. The VAT Calculator holds no country rates: you enter the rate that applies to you, so there is no official figure for Numerila to keep up to date.
Precision: calculation versus display
A tool's internal calculation always uses the full precision available; only the displayed figure is ever rounded for readability. Numerila does not round a value before calculating with it, and a genuinely non-zero result is never allowed to display as if it were zero.
Unit distinctions that matter
Where two units share a name but differ in definition, Numerila keeps them distinct rather than guessing which one a reader means. US and Imperial units (a US cup and an Imperial pint are not the same size) are always labelled explicitly. Decimal data units (kilobytes, using powers of 1000) and binary data units (kibibytes, using powers of 1024) are never conflated, since this is a common and genuine source of error elsewhere.
No guessed conversions
The Cooking Unit Converter never converts between a mass unit and a volume unit, because doing so correctly requires an ingredient's density (a cup of flour and a cup of sugar do not weigh the same), and Numerila does not assume or estimate one.
Dates and calendars
Every date tool on Numerila uses the proleptic Gregorian calendar (the ordinary modern calendar, projected backwards for dates before it was actually adopted) and supports years 1 to 9999. There is no year 0 and no BCE/BC support. Each date and duration tool states its own counting convention explicitly (for example, whether a day count is inclusive or exclusive, and how adding a month clamps to the end of a shorter target month), since these conventions genuinely differ between tools.
Numbers and locale
Numbers you type are parsed in a locale-aware way, and an integer that would silently lose precision as an ordinary number is rejected rather than quietly rounded. A tool's internal calculation keeps full precision throughout; only the final displayed figure is rounded for readability.
Randomness
Every Numerila tool that generates a random value (numbers, list picks, passwords, UUIDs) uses your browser's built-in cryptographic random number source, not an ordinary pseudo-random generator. Random tools have not been independently audited for regulated or security-sensitive processes.
AI-assisted editorial work
AI tools may be used to assist with research, drafting, organisation and quality checks. Content is not published solely because an AI system produced it. Relevant formulas, implementation behaviour, sources and important claims are checked before publication.
Testing
Every calculator's logic is covered by an automated test suite, checked against independently verified expected results rather than against its own output. This is how a genuine defect, once found, is prevented from silently returning in a later change. See the Corrections Policy for how a specific reported error is handled.
Independence from advertising and affiliate influence
No tool's method, wording, or result is influenced by advertising or affiliate relationships. Numerila does not currently run advertising or affiliate programmes at all, and no calculator will ever be adjusted to favour a commercial outcome. See the Privacy Policy for the site's current position.
Corrections
If you believe a calculation, source citation, or explanation is wrong, see the Corrections Policy for how to report it and how it will be investigated.