How we build and verify our calculators
Trust in a financial tool should come from process, not vibes. This page documents the four rules every calculator on stockcalculator.in follows before it goes live — and after, for as long as it stays up.
1. Formulas come from standard definitions
Each calculator implements one standard financial definition — compound annual growth rate, weighted average purchase price, holding-period capital gains, and so on. The formula appears on the tool's own page in plain language, followed by a worked example whose arithmetic you can reproduce on paper. Where a genuine convention choice exists (for example, annualising partial years), the page says which convention it uses.
2. Math is tested before it ships
Calculation logic is written as pure functions and locked behind an automated test suite with a 100% coverage requirement on the calculation layer. Tests explicitly include zero inputs, negative inputs, unrealistically large values, and India-specific boundaries such as exemption thresholds and holding-period cut-offs. A calculator page does not render until its function passes.
3. Rates carry a source and a date
Figures that can change — tax rates, exemption thresholds, securities transaction tax, exchange charges, stamp duty, brokerage schedules — are stored in versioned data files rather than buried in code. Each entry records three things: the value, the official source URL (the Income Tax Department, the relevant exchange or depository, SEBI, or the broker's own pricing page), and the date we verified it. Pages display these sources in their data-sources section. We do not fill such numbers from memory; they are looked up at build time.
4. Pages state their age honestly
Every calculator shows its author and a last-updated date, and that date reflects content review — not cosmetic edits. When a cited figure changes upstream, the affected page is re-verified, updated, and re-dated. Corrections reported by readers are handled the same way; send them to editor@stockcalculator.in.
What these tools are not
They are estimation aids, not filing software or advice. Real transactions involve round-trip timing, corporate actions, broker-specific rounding, and grandfathering rules that a general-purpose calculator cannot fully model. Treat outputs as planning-grade, then confirm anything material with your broker, fund house, or a qualified professional — our disclaimer expands on this.