How we build and verify our tools

ReckonBox is a new, independent site, so we do not ask you to trust a famous name. We ask you to check our work. Every calculator shows the formula it runs, cites the sources behind its numbers, and is tested against known results before it goes live. This page explains exactly how that happens, so you can judge the method rather than take the result on faith.

Every tool shows the formula it runs

Each calculator page carries a "how it works" section with the real formula, down to the compounding frequency. If a fixed deposit compounds quarterly, the page shows M = P(1 + r/4) to the power 4t and walks through a worked example with actual numbers. None of the math hides behind the result, so you can reproduce any figure by hand or in a spreadsheet.

We research the numbers live, never from memory

Every rate, limit, threshold, and rule on a tool comes from a source we read while building that tool. We do not fill gaps from memory or a general impression. For a scheme like the National Savings Certificate or Atal Pension Yojana, the current government rate, the contribution chart, and the tax rules are taken from official and primary sources and cited on the page itself.

When sources disagree, we reconcile them and use the authoritative one. On the Kisan Vikas Patra page, for example, we show the correct 115-month doubling period, which is 9 years and 7 months, even though several popular pages print it as 9 years 5 months. We lean on primary sources: government departments and regulators such as India Post, the PFRDA, the RBI and the income tax department, along with official scheme documents. Where a bank or provider sets the rate, we make it a field you control, so a stale default never decides your result.

We test the math before it ships

Every formula is written as code with automated tests that check it against figures already known to be correct. The fixed deposit formula is tested against the maturity value ClearTax publishes for the same inputs; the recurring deposit formula is checked against Groww's worked example to the rupee; the SIP, PPF and pension formulas are each pinned to reference numbers. If a change breaks any of those checks, it does not ship. While researching a tool we also cross-check its output against the leading calculators and any official worked example, which is how we catch the errors that other pages carry.

We date every rate and refresh it when it changes

Interest rates and tax thresholds move, so each tool carries a visible last-updated date, and rate-sensitive pages state the quarter or financial year a figure applies to. When the government revises a small-savings rate or a bank changes its deposit rate, the number that actually decides your result is the one you enter. We update the stated defaults and rules when the underlying source changes.

Estimates, not advice

Our tools explain what something is and how its math works. They do not tell you what to do with your money, your health, or your legal position. A maturity value or a pension figure is an estimate based on your inputs and the current rules, not a recommendation, and tax outcomes in particular depend on your own situation. For a decision that matters, talk to a qualified professional such as a chartered accountant or a SEBI-registered adviser.

How these tools are made

ReckonBox is built and reviewed by the developers at DexTechLabs, the software company that operates it. We use AI as a drafting tool, under our direction: it helps write the first pass, and we verify everything it produces. Every formula is unit tested against known values, every fact is traced to a cited source, and every page is checked against a written set of rules before it publishes. Telling you that, and then showing the testing and sourcing behind it, is the honest version of "trust us".

Your numbers stay on your device

Every calculator runs in your browser. You do not sign in, and the values you type are not sent to us or to anyone else. That is a privacy choice, and it is also why the tools respond instantly and keep working offline once the page has loaded.

Found a mistake?

If a number looks wrong or a rule has changed, tell us and we will check the source and fix it. Accuracy is the whole point of the site, so a correction from a reader is genuinely welcome. You can reach us through the contact page.