Formulas on every page
Each calculator states the formula it uses under "About this tool". Loans use the standard reducing-balance EMI formula; deposits use the compounding rules of the scheme (quarterly for bank FDs, yearly for PPF, SSY and NSC); SIPs assume investment at the start of each month.
Official rates, editable
Small-savings rates are pre-filled from the Q2 (Jul–Sep 2026) notification (FY 2026-27): PPF 7.1%, SSY 8.2%, SCSS 8.2%, NSC 7.7%, KVP 7.5%, POMIS 7.4%. Income tax uses the FY 2026-27 slabs. Every rate stays editable because they change.
What we don't model
Unless a page says otherwise: income-tax surcharge, state-specific stamp duty, lender-specific rounding and day counts, and market volatility. Pages note the main limits next to the result.
Checks
Formulas are tested against worked examples and official illustrations, such as the Income Tax Department's tax tables and lenders' published EMI schedules, before release and whenever rules change.
Corrections
If a result looks wrong, tell us the inputs and the source you are comparing with. We check it and fix the page if needed.