Methodology
Every calculator here follows the same process, so you can judge for yourself how far to trust a number.
1. A written specification first
Before any interface exists, each tool gets a specification: its inputs and allowed ranges, the exact formulas, and every convention spelled out. For money tools that includes how an annual rate becomes a monthly one, whether payments happen at the start or the end of a period, and when rounding happens.
2. Golden values worked out independently
For each tool we record a table of "golden" cases whose answers were worked out outside the site's own code, using at least two methods (for example a closed-form formula and a period-by-period simulation, in a separate language). The tool's code must reproduce every golden value to within one paisa. A tool whose test values came from the same code it is testing does not ship.
3. Property and round-trip tests
Beyond fixed examples, automated tests check properties that must always hold. For the SIP calculator, these include: with a 0% return the value equals what you put in; doubling the monthly amount exactly doubles the value; a higher return, a longer period or a larger amount never lowers the result; and solving for the SIP a goal needs, then running that SIP forward, lands back on the goal.
4. Conventions we use
- Money is calculated in rupees with full precision and rounded only for display.
- Indian digit grouping (₹12,34,567) and lakh/crore in words.
- Monthly compounding. Where a tool offers a choice, "nominal" divides the annual rate by 12 and "effective" uses the monthly rate that compounds to the annual rate exactly. The convention in use is shown under every result.
- Dates appear as "21 Oct 2026". Each page shows when it was last reviewed.
5. What our numbers do not include
Unless a tool says otherwise, results exclude tax, fees, loads and charges, and assume a steady rate of return. Real returns are uneven and can be negative. Each tool lists its own exclusions next to the result.
6. Sources
Formulas and rules are checked against primary sources (regulators such as SEBI and RBI, official documents, or standard textbooks). Each tool page lists its sources with the date they were last checked.
7. Reviews and corrections
Money tools are reviewed at least once a year and after relevant regulatory changes. Each page shows its last review date and a changelog. If you spot a problem, please tell us; corrections are logged, never made silently.