How we check our formulas

Every calculator on this site was AI-generated, then put through the same five-step pipeline before it went live. No competitor publishes this — we do, because the honest version of the process is a better claim than an inflated one.

The pipeline

1. Source lookup. The formula is sourced from a named authority — a government tax schedule, an engineering standard, a peer-reviewed reference, or a well-established mathematical identity. That source and the date it was checked are recorded on the calculator itself.
2. AI review. A second AI agent (Fable 5.1) independently reviews the formula, worked example, and edge cases against the cited source.
3. Golden-value test assertions. Every calculator has hand-written test cases with known-correct inputs and outputs, run automatically (npm run test:calc) on every change. A calculator that fails its own tests doesn't ship.
4. Human spot-check. A person reviews the formula, the source, and the edge cases before publication.
5. Source and date, on every page. Each calculator shows exactly what it was checked against and when — so you can judge the source yourself instead of taking our word for it.

What this is not

This is not the same claim as "hand-checked" or "human-verified" end to end — those would mean a person independently re-derived every formula from scratch, which isn't what happened here. AI-generated, AI-reviewed, automatically tested, and spot-checked by hand is a different — and more accurate — claim. A calculator that has genuinely been reviewed line by line by a person says so explicitly on that page.

Statutory calculators change

India's tax and statutory calculators (income tax, GST, HRA, EPF, and similar) are re-checked every year after the Union Budget, since the rules they encode change on a fixed schedule.

What we track

No ad network, no cookies for analytics, and nothing that follows you to other sites. What we do run is counting: how many people opened a calculator, how many are on the site right now, which pages and explanations get used, and whether a calculator did its job — someone tried a second set of numbers, took the answer away, or couldn't enter a number it should take — never the numbers themselves. That is Cloudflare's beacon, DataFast in its cookieless mode, and our own counters, which tell visits apart with a hash that changes every day rather than an identifier stored on your device. None of them can recognise you on a later day. The one exception is a payment: if you pay us, DataFast records it against Dodo's reference for you as a customer.

This page used to say "no cookies" while the visitor counters set them, and from September 2026 the site asked before running them. Since 14 October 2026 nothing sets an analytics cookie, so there is no question to ask. The details, including the three per-tab entries DataFast keeps, are in the Privacy Policy, which also has a "Don't count my visits" switch.

Something looks wrong?

Use the "Spotted a mistake? Tell us" link on any calculator page, which opens the contact form with the calculator filled in, or see the Editorial Standards page for how corrections are handled.