How our calculators work
Every calculator follows the same process, so you know what is behind a number before you rely on it.
1. A standard formula, shown on the page
We start from a well-known formula, such as the reducing-balance formula for EMI or the future value of an annuity for a SIP. The formula is written out on each calculator page with every variable explained.
2. Clear inputs and assumptions
Each input is a visible field you can change. Starting values are examples, not recommendations. Each page lists the assumptions behind the result, for example that a rate stays fixed or that deposits are made at the start of the month.
3. Testing
We check key results against independent calculations. For example, the EMI, SIP, FD, bond price, Black-Scholes and GST calculators are compared with separately computed values. We also test unusual inputs: blank fields, zero, very large numbers and values that should produce an error. A calculator should show a clear error or a dash, never a misleading number.
4. Tax and rate-dependent calculators
Tax slabs, rebates, deductions, scheme interest rates and GST rates are set by governments and change over time. Pages that depend on them state the rules and year used, and show the date they were last reviewed. Where a rate changes often, such as the PPF interest rate, the value in the calculator is only an editable example and we ask you to check the current rate.
5. Updates and corrections
We review tax and rate-dependent pages when the rules change and update the date on the page. If you report an error, we check it against the formula and sources and correct the page if needed. Use the error report form.
What the results mean
A result is an estimate based on the numbers and assumptions on the page. It is not a quote from a lender, a forecast of investment returns or professional advice. See the disclaimer and the sources we use.