Editorial and testing policy
A calculator is only useful if you can trust it. This page explains how we make sure ours are right — and what we do when they are not.
1. Start from the source
Every tool is built from its defining formula, standard or rule. Unit factors use the exact legal definitions (for example, 1 lb = 0.45359237 kg). Tools based on laws, tax rates or health guidance are researched from official sources — government portals, tax authorities, standards bodies and public-health organizations — and those sources are linked on the page.
2. Separate, tested calculation code
The math behind each tool lives in its own module, apart from the page design, and is covered by automated tests. Tests compare results with reference values we work out independently, and include awkward cases: zero and negative inputs, leap years, month ends, rounding boundaries and very large numbers. The whole test suite runs before every release.
3. Show the working
Results are displayed with the formula and the steps, using the visitor's own numbers. This makes errors visible — to us and to you — and helps people understand the answer rather than copy it.
4. Be clear about limits
Where a result is an estimate (for example, an end-of-service gratuity or a BMI category), we say so, explain what the calculation leaves out, and point to the authority that makes the final determination. Our tools are for information and do not replace professional financial, legal or medical advice.
5. Review and update
Each tool page shows the date it was last reviewed. Pages that depend on rates or rules that can change — such as VAT rates or labor-law provisions — are re-checked at least once a year and whenever we learn of a change.
6. Corrections
If you find an error, please contact us. We investigate every report, fix confirmed errors as a priority, and update the review date on the page.
7. Advertising and independence
Reeliy may show ads to stay free. Advertisers have no influence over our tools or content, ads are labeled, and they are never placed between a calculator's inputs and its result.
8. Use of automation
We use software, including AI-assisted drafting and coding tools, to help build pages. Every formula, figure and source is checked, and every tool must pass its reference tests before it is published.