Calculator Methodology

1. How calculators are created

Each calculator begins with a single, well-defined real-world question — e.g. What will my Post Office RD mature to? We then write a pure compute function, a transparent input schema, a worked example and a set of FAQs. UI, analytics and SEO are added by shared infrastructure so every calculator behaves identically.

2. Formula selection process

• Start from the official formula published by the regulator, scheme operator or standards body.
• Where multiple conventions exist (e.g. compounding frequency), we use the convention most commonly applied by the operator and disclose it on the page.
• Approximations are only used when the exact formula is impractical for a calculator UI; in that case the page states the assumption explicitly.

3. Validation standards

Every formula is implemented as a pure function with unit tests covering normal cases, boundary cases and invalid inputs. Each numeric example shown on the page is independently reproduced by the test suite. See How We Verify Formulas for the full review checklist.

4. Source verification process

We rely on primary sources only:

• Government departments (Ministry of Finance, Ministry of Communications, RBI, IRDAI, SEBI, IRS, HMRC, ATO).
• Scheme operators (India Post, EPFO, NPS Trust, banks' published rate cards).
• Recognised standards bodies (ISO, NIST, WHO for health metrics).

We do not cite secondary aggregators or unattributed blog posts. Every calculator page lists the official references used.

5. Quality assurance process

• Automated unit tests run on every code change.
• Edge-case tests cover zero, negative and out-of-range values.
• Mobile rendering, accessibility (keyboard + screen reader) and SEO metadata are checked before release.
• Statutory rates and limits are reviewed when the issuing body publishes a change and at least once per quarter.