How we build & verify every calculator

Our Methodology

AllSmartCalculators is built on one promise: every result you see has been worked out using a formula we can defend with a primary source, and reviewed by a human before going live. This page explains how each calculator is researched, built, tested and updated.

Primary Sources We Rely On

For finance calculators (EMI, SIP, PPF, NPS, home loan), we follow guidance from the Reserve Bank of India (RBI), the Securities and Exchange Board of India (SEBI), and rate notifications from the Ministry of Finance. For GST, TDS and income tax tools, we use the official GSTN portal, the Income Tax Department of India and the CBDT circulars.

For health calculators (BMI, BMR, calorie needs, pregnancy due date), we reference the World Health Organization (WHO), the Indian Council of Medical Research (ICMR) for India-specific BMI bands, the CDC for pregnancy and child growth, and standard nutrition science formulas like Harris-Benedict and Mifflin-St Jeor.

For unit conversions, scientific and engineering tools, we use NIST (National Institute of Standards and Technology) and the International System of Units (SI). For insurance and IRDAI-regulated products, we use IRDAI circulars. For crypto tools, we follow public exchange rate feeds and standard volatility formulas.

Editorial Principles

Every calculator goes through four stages. Research: we collect formulas from at least two independent sources and cross-check them. Build: a developer codes the formula and adds input validation in rupees, kilograms or other India-friendly units. Review: a second team member tests the calculator with at least five real-world inputs (small, large, edge cases). Publish: only after review do we ship the calculator with a tips section, worked example and accuracy note.

Updates and Corrections

Rates change. PPF interest is revised quarterly. Income tax slabs change every Union Budget. GST rates can shift by notification. We monitor official sites and update the affected calculators within a reasonable window. If you spot an error or an outdated rate, write to allsmartcalculators@gmail.com and we will fix it.

Limitations

Our calculators give estimates, not personalised financial, medical or legal advice. Always cross-check important decisions with a qualified professional. We make money through Google AdSense, which lets us keep the tools free for everyone.

Last reviewed: 20 May 2026.