How Equatara builds and checks calculators

From question to published calculator

1. Define the task. We identify one clear user problem, audience, units, locale, jurisdiction, and intended outcome.
2. Specify the method. We record the formula or decision rules, symbols, valid ranges, assumptions, rounding, dates, and exclusions.
3. Collect evidence. Material formulas, constants, conversions, warnings, and source-defined limits are mapped to precise source locations.
4. Implement a version. The code is bound to an immutable formula identifier and semantic version such as 1.0.0.
5. Test behavior. Known answers, boundaries, missing and invalid inputs, decimals, units, and risk-specific comparisons are checked.
6. Review the whole page. Formula, content, accessibility, privacy, source currency, and specialist requirements must pass.
7. Publish deliberately. Drafts remain noindex. A page becomes indexable only after the release gate is approved.
8. Monitor and correct. Source changes, feedback, failures, and scheduled reviews can trigger an update, withdrawal, or return to noindex.

Which sources we use

We prefer the strongest current authority available for the claim:

1. laws, regulations, government publications, official datasets, and standards bodies;
2. peer-reviewed research, professional guidelines, and recognized technical standards;
3. university textbooks, established reference works, and professional associations;
4. documented independent derivations checked against authoritative definitions and independent implementations.

Competitor calculators can help us understand terminology or user demand, but they are not formula authority. AI output is not a source and cannot approve its own work. We record the source organization, title, link or identifier, exact locator, access date, jurisdiction, effective period, and the claim it supports.

Review increases with risk

These are maximum intervals, not promises that a rule remains current until the deadline. Known effective dates, volatile data, a withdrawn source, or a credible correction trigger an earlier review. A high-risk calculator stays unpublished when the required review is missing.

How we test calculations

• Known-answer examples tied to the exact formula version
• Minimum, maximum, zero, negative, decimal, and empty-input cases where applicable
• Impossible and unsupported inputs that must fail with a useful message
• Unit-conversion round trips and exact conversion factors
• Independent comparison for higher-risk tools
• Regression tests so an unrelated change cannot silently alter approved behavior

Tests reduce errors but cannot prove that a model fits every real situation. Each calculator also explains what it includes, excludes, assumes, and rounds.

Formula versions and changes

An approval applies only to the exact formula version, evidence set, jurisdiction, and effective period reviewed. A material formula change creates a new version and must pass its tests and reviews again. Historical approval is not silently transferred to new logic.

A current page shows its formula version and verification date. Dated or rule-based tools also identify their applicable period. If authority expires or materially changes, the page is updated, archived, withdrawn, or made noindex until it is safe to use again.

What every calculator page should explain

• its purpose, necessary inputs, result units, and plain-language interpretation;
• the formula or algorithm, symbol definitions, and calculation steps;
• at least two original, checked examples;
• assumptions, rounding, edge cases, warnings, and what the result cannot determine;
• sources, review information, last verification date, and related next-step tools.

We do not publish raw AI-generated copy, copy competitors, pad pages to a word count, or make thin pages for trivial keyword and unit variations. Localized pages require complete human review; unfinished translations stay noindex.

Privacy and commercial independence

Basic calculations require no account. Sensitive raw inputs and results should not enter analytics or share URLs by default. Advertising, sponsorship, and affiliate relationships cannot change a formula, result, evidence choice, review decision, or correction outcome.

Report a problem

If a formula, result, example, source, explanation, or accessibility feature appears wrong, use our correction route. Include the calculator name, what you expected, and a source if you have one. Do not send sensitive input values. A credible report can trigger immediate review and temporary removal from indexing.

Public guidance behind this policy

• Google Search: creating helpful, reliable, people-first content
• Google Search spam policies
• Bing Webmaster Guidelines

These search guidelines inform publication quality; they are not sources for calculator formulas.